This file was created by the TYPO3 extension publications --- Timezone: CEST Creation date: 2026-06-03 Creation time: 05:10:11 --- Number of references 80 article Daskalopoulou2025 Article 2025 10.1016/j.chemgeo.2025.122722 Chemical Geology 681 https://www.scopus.com/inward/record.uri?eid=2-s2.0-105000277412&doi=10.1016%2fj.chemgeo.2025.122722&partnerID=40&md5=cb65907b9cb2d6b9bb9aff47a1dd9b4b Cited by: 0; All Open Access, Hybrid Gold Open Access Kyriaki Daskalopoulou Samuel Niedermann Franziska D.H. Wilke Martin Zimmer Heiko Woith Johannes Glodny Wolfram H. Geissler Horst Kämpf article Rapprich2024113 The sequence of alkaline basaltic lavas and associated pyroclastic deposits that fill Bažina maar in western Bohemia is transected by a vein of apatite-dominated rock revealed in the S4 borehole. Aside from solid vein fill, apatite also impregnates a significant part of the drilled volcanic sequence. In the main body (depth 60.00–66.60 m), apatite occurs in two texturally distinct types: common cauliflower-type apatite (type 1) is transected by veinlets of coarser (0.2 mm long) apatite crystals (type 2). Both types have grown into open spaces suggesting precipitation from fluids rather than crystallization from melt, which is consistent with generally low trace element contents with slight enrichment in Cs, Sr, U and Pb. Relative to other local Plio-Pleistocene volcanic rocks, apatite vein-fill is shifted in87Sr/86Sr towards more radiogenic values (0.7053–0.7054). This suggests that fluids carrying mantle-derived ions mixed with groundwater interacting with granitic country-rock, as also evidenced by the purely crustal character of noble gases trapped in apatite. Unlike the mofettes occurring along the Mariánské Lázně Fault on the eastern margin of the Cheb Basin, the4He/3He ratios from Bažina apatite do not indicate mantle noble gas contribution. According to our model, the originally Sr–P-rich fluids with low87Sr/86Sr mixed with Cs–U-enriched groundwater circulating in country-rock granites with radiogenic 87 Sr/86Sr. Therefore, present-day CO2 outgassing through mofettes related mainly to the Mariánské Lázně Fault (eastern margin of the Cheb Basin) is likely independent of, and unrelated to, volcanism of the Cheb–Domažlice Graben. © 2024, Czech Geological Survey. All rights reserved. Article 2024 10.3190/jgeosci.392 Journal of Geosciences (Czech Republic) 69 Czech Geological Survey 113 – 127 2 Czech Republic; apatite; enrichment; igneous geochemistry; maar; noble gas; penetration; Pleistocene; precipitation (chemistry); strontium isotope; volcaniclastic deposit https://www.scopus.com/inward/record.uri?eid=2-s2.0-85202567467&doi=10.3190%2fjgeosci.392&partnerID=40&md5=f7345350702859456751e61d5ad6b7a5 Cited by: 0 Vladislav Rapprich Tomáš Vylita Kata Molnár John M. Hora Zsolt Benkó Michal Čurda Tomáš Magna Magdaléna Koubová Ondřej Pour Pavla Hrubcová Tomáš J. Fischer article WOS:001194368500001 2024 10.1002/nsg.12293 NEAR SURFACE GEOPHYSICS 22 298-312 3 borehole; seismic array; tomography; traveltime Nikolaus Rein Marius P. Isken Dorina Domigall Matthias Ohrnberger Katrin Hannemann Frank Krueger Michael Korn Torsten Dahm article Lipus2024 Article 2024 10.1186/s40793-024-00651-9 Environmental Microbiome 19 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85212844735&doi=10.1186%2fs40793-024-00651-9&partnerID=40&md5=4a52e594919b818c2f50d86a3e38ad67 Cited by: 0; All Open Access, Gold Open Access Daniel Lipus Zeyu Jia Megan Sondermann Robert Bussert Alexander Bartholomäus Sizhong Yang Dirk Wagner Jens Kallmeyer article Jia2023 Article 2023 10.3389/fmicb.2023.1105259 Frontiers in Microbiology 14 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85161200278&doi=10.3389%2ffmicb.2023.1105259&partnerID=40&md5=94b72dda4a22c5ca095d81e00ac5436b Cited by: 6; All Open Access, Gold Open Access, Green Open Access Zeyu Jia Daniel Lipus Oliver Burckhardt Robert Bussert Megan Sondermann Alexander Bartholomäus Dirk Wagner Jens Kallmeyer article WOS:001042207400001 2023 10.1029/2023EA003009 EARTH AND SPACE SCIENCE 10 8 maar-diatreme volcano; magnetometry; electrical resistivity tomography; drilling; gravity survey; Eger Rift Pavla Hrubcová Tomáš Fischer Vladislav Rapprich Jan Valenta Petr Tábořík Jan Mrlina Torsten Dahm Tomáš Vylita Roman Beranek Radek Klanica Josef Vlček Veronika Turjaková article Woith2023 Mofettes are gas emission sites where high concentrations of CO2 ascend through conduits from as deep as the mantle to the Earth’s surface and as such provide direct windows to processes at depth. The Hartoušov mofette, located at the western margin of the Eger Graben, is a key site to study interactions between fluids and swarm earthquakes. The mofette field (10 mofettes within an area of 100 m × 500 m and three wells of 28, 108, and 239 m depth) is characterized by high CO2 emission rates (up to 100 t/d) and helium signatures with (3He/4He)c up to 5.8 Ra, indicating mantle origin. We compiled geological, geophysical, geochemical, and isotopic data to describe the mofette system. Fluids in the Cheb basin are mixtures between shallow groundwater and brine (>40 g/L at a depth of 235 m) located at the deepest parts of the basin fillings. Overpressured CO2-rich mineral waters are trapped below the mudstones and clays of the sealing Cypris formation. Drilling through this sealing layer led to blow-outs in different compartments of the basin. Pressure transients were observed related to natural disturbances as well as human activities. External (rain) and internal (earthquakes) events can cause pressure transients in the fluid system within hours or several days, lasting from days to years and leading to changes in gas flux rates. The 2014 earthquake swarm triggered an estimated excess release of 175,000 tons of CO2 during the following four years. Pressure oscillations were observed at a wellhead lasting 24 h with increasing amplitudes (from 10 to 40 kPa) and increasing frequencies reaching five cycles per hour. These oscillations are described for the first time as a potential natural analog to a two-phase pipe–relief valve system known from industrial applications. © 2022 by the authors. Article 2023 English 20763263 10.3390/geosciences13010002 Geosciences (Switzerland) 13 MDPI 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85146749742&doi=10.3390%2fgeosciences13010002&partnerID=40&md5=44c99376ec52eefb4b9cb40f3691b295 Cited by: 0; All Open Access, Gold Open Access, Green Open Access Heiko Woith Josef Vlček Tomáš Vylita Torsten Dahm Tomáš Fischer Kyriaki Daskalopoulou Martin Zimmer Samuel Niedermann Jessica A. Stammeier Veronika Turjaková Martin Lanzendörfer article Platz2022 The region of West Bohemia and Upper Palatinate belongs to the West Bohemian Massif. The study area is situated at the junction of three different Variscan tectonic units and hosts the ENE-WSW trending Ohře Rift as well as many different fault systems. The entire region is characterized by ongoing magmatic processes in the intra-continental lithospheric mantle expressed by a series of phenomena, including e.g. the occurrence of repeated earthquake swarms and massive degassing of mantle derived CO2 in form of mineral springs and mofettes. Ongoing active tectonics is mainly manifested by Cenozoic volcanism represented by different Quaternary volcanic structures. All these phenomena make the Ohře Rift a unique target area for European intra-continental geo-scientific research. With magnetotelluric (MT) measurements we image the subsurface distribution of the electrical resistivity and map possible fluid pathways. Two-dimensional (2D) inversion results by Muñoz et al. (2018) reveal a conductive channel in the vicinity of the earthquake swarm region that extends from the lower crust to the surface forming a pathway for fluids into the region of the mofettes. A second conductive channel is present in the south of their model; however, their 2D inversions allow ambiguous interpretations of this feature. Therefore, we conducted a large 3D MT field experiment extending the study area towards the south. The 3D inversion result matches well with the known geology imaging different fluid/magma reservoirs at crust-mantle depth and mapping possible fluid pathways from the reservoirs to the surface feeding known mofettes and spas. A comparison of 3D and 2D inversion results suggests that the 2D inversion results are considerably characterized by 3D and off-profile structures. In this context, the new results advocate for the swarm earthquakes being located in the resistive host rock surrounding the conductive channels; a finding in line with observations e.g. at the San Andreas Fault, California. © 2022 The Authors Article 2022 English 00401951 10.1016/j.tecto.2022.229353 Tectonophysics 833 Elsevier B.V. Bohemian Massif; Electric conductivity; Magnetotellurics; Strike-slip faults; Structural geology; Volcanoes; 2-d inversions; Conductive channels; Earthquake swarms; Fluid pathways; Fluid/magma reservoir; Inversion results; Magma reservoirs; Ohře rift; Study areas; Volcanic structures; earthquake swarm; electrical resistivity; magnetotelluric method; Quaternary; rift zone; three-dimensional modeling; volcanism; volcanology; Earthquakes https://www.scopus.com/inward/record.uri?eid=2-s2.0-85129433829&doi=10.1016%2fj.tecto.2022.229353&partnerID=40&md5=4a99639dfcf40b15fc518d9144df8ff4 Cited by: 2; All Open Access, Green Open Access, Hybrid Gold Open Access Anna Platz Ute Weckmann Josef Pek Světlana Kováčiková Radek Klanica Johannes Mair Basel Aleid article Isken2022944 Article 2022 10.1093/gji/ggac229 Geophysical Journal International 231 944 – 949 2 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85135204437&doi=10.1093%2fgji%2fggac229&partnerID=40&md5=e0f5207d9c623baad96d980d36e07f9b Cited by: 12; All Open Access, Green Open Access Marius Paul Isken Hannes Vasyura-Bathke Torsten Dahm Sebastian Heimann article RN261 Journal Article 2022 1816-3459 10.5194/sd-31-31-2022 Scientific Drilling 31 31-49 Tomáš Fischer Pavla Hrubcová Torsten Dahm Heiko Woith Tomáš Vylita Matthias Ohrnberger Josef Vlček Josef Horálek Petr Dědeček Martin P. Lipus Jens Kallmeyer Frank Kruger Katrin Hannemann Michael Korn Horst Kämpf Thomas Reinsch Jakub Klicpera Daniel Vollmer Kyriaki Daskalopoulou article Daskalopoulou2021 The Cheb Basin (Czech Republic) is characterized by emanations of magma-derived gases and repeated occurrences of mid-crustal earthquake swarms with small to intermediate magnitudes (ML < 4.5). Associated intense mantle degassing occurs at the Hartoušov Mofette, a representative site for the Cheb Basin. Here, we performed 14 sampling campaigns between June 2019 and March 2020. Gas samples of fluids ascending in two boreholes (F1, ∼28 m depth and F2, ∼108 m depth) and from a nearby natural mofette were analyzed for their chemical (CO2, N2, O2, Ar, He, CH4, and H2) and isotope compositions (noble gases and CO2). CO2 concentrations were above 99.1% in most samples, while O2 and N2 were below 0.6%. He ranged from 19 to 34 μmol/mol and CH4 was mostly below 12 μmol/mol. Isotope compositions of helium and carbon in CO2 ranged from 5.39 to 5.86 RA and from −2.4 to −1.3 ‰ versus VPDB, respectively. Solubility differences of the investigated gases resulted in fluctuations of their chemical compositions. These differences were accompanied by observed changes of gas fluxes in the field and at the monitoring station for F1. Variations in solubilities and fluxes also impacted the chemical concentration of the gases and the δ13C values that were also likely influenced by Fischer-Tropsch type reactions. The combination of (a) the Bernard ratio, (b) CH4/3He distributions, (c) P-T conditions, (d) heat flow, and (e) the sedimentary regime led to the hypothesis that CH4 may be of mixed biogenic and volcanic/geothermal origin with a noticeable atmospheric contribution. The drilling of a third borehole (F3) with a depth of ∼238 m in August 2019 has been crucial for providing insights into the complex system of Hartoušov Mofette. © Copyright © 2021 Daskalopoulou, Woith, Zimmer, Niedermann, Barth, Frank, Vieth-Hillebrand, Vlček, Bağ and Bauz. Article 2021 English 22966463 10.3389/feart.2021.615766 Frontiers in Earth Science 9 Frontiers Media S.A. Cheb Basin; Czech Republic; Karlovarsky; Atmospheric movements; Boreholes; Chemical analysis; Earthquakes; Inert gases; Isotopes; Solubility; Atmospheric contributions; Chemical compositions; Chemical concentrations; CO2 concentration; Crustal earthquakes; Isotope compositions; Monitoring stations; Sampling campaigns; carbon; carbon dioxide; carbon flux; concentration (composition); degassing; helium; isotopic composition; magma; mantle structure; solubility; Carbon dioxide https://www.scopus.com/inward/record.uri?eid=2-s2.0-85104633463&doi=10.3389%2ffeart.2021.615766&partnerID=40&md5=cc9df0aed8ef6b1d4e6b3ec7da6cac66 Cited by: 3; All Open Access, Gold Open Access, Green Open Access Kyriaki Daskalopoulou Heiko Woith Martin Zimmer Samuel Niedermann Johannes A. C. Barth Alexander H. Frank Andrea Vieth-Hillebrand Josef Vlček Cemile Dilara Bağ Ralf Bauz article Stebich2020 Palaeoecological evidence of intra-Saalian warm stages in Central Europe, which was strongly affected by glacial and periglacial processes during the major Middle and Late Pleistocene cold periods, is ambiguous so far. Recently, the first continuous sedimentary sequence of Central Europe containing the Saalian complex (MIS 8–6) with the Eemian interglacial in stratigraphic superposition was recovered from the newly discovered Neualbenreuth Maar (NE-Bavaria). Here we present palynological results from this record allowing us to critically discuss the available biostratigraphical evidence of alternating intra-Saalian warm-cold intervals from Central Europe. The new pollen record from the Neualbenreuth Maar comprises a continuous record of vegetation and climate changes encompassing four warm stages and five cold periods. The dominance of cold and dry tolerant herbs and the sparse representation of pioneer trees and shrubs during most parts of the sequence indicate open landscapes of steppe to woody-steppe character typical of late Middle and Late Pleistocene glacial periods in Central Europe. The pollen assemblages of the warm stage in the upper part of the core clearly support its correlation with the Eemian interglacial. The three pre-Eemian warm stages represent terrestrial analogues of the marine isotope stages (MIS) 7e, 7c, and 7a. During each of these intervals forests were established, but the reduced abundances and lower diversity of thermophilous and sub-oceanic elements in comparison to the Eemian attest to a weak interglacial character. Each of these interglacials shows a similar vegetation succession and only minor differences in the vegetation composition. The intervening stadial periods represent a strong (MIS 7d) and a moderate (MIS 7b) climate deterioration, respectively. The vegetation and climate succession during the Saalian glacial-interglacial complex of Neualbenreuth is broadly in line with the respective palynological signature from the Velay record (French Massif Central) and the Hoogeveen interstadial (The Netherlands). In contrast, there is only limited correspondence with most pollen records from northern and southern Central Europe, which were hitherto classified as MIS 7. © 2020 Elsevier Ltd Article 2020 English 02773791 10.1016/j.quascirev.2020.106681 Quaternary Science Reviews 250 Elsevier Ltd Europe; Climate change; Deterioration; Stratigraphy; Vegetation; Climate deterioration; Marine isotope stages; Middle Pleistocene; Periglacial process; Sedimentary sequence; Sparse representation; Vegetation composition; Vegetation successions; allostratigraphy; Eemian; interglacial; interstadial; paleoecology; palynology; Pleistocene; Pliocene-Pleistocene boundary; Saalian; stratigraphy; Glacial geology https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096179678&doi=10.1016%2fj.quascirev.2020.106681&partnerID=40&md5=3d41827b4e6348f9f1280a947c7cb21b Cited by: 4 Martina Stebich Dana Höfer Jens Mingram Norbert Nowaczyk Johann Rohrmüller Jan Mrlina Horst Kämpf article Lied20201707 Tephra layers of the Mýtina Maar, Czech Republic, contain ferrimagnetic Mg–Al-rich titanomagnetite, which is suggested to originate from a fractionated alkaline CO2-rich lithospheric mantle melt. We investigated the magnetic mineralogy and Curie temperature (TC) from tephra deposits of two drill cores (< 9 m depth). TC calculated (208 ± 14 °C) from chemical composition (Fe2+0.8Mg0.5Fe3+1.1Al0.3Ti0.3O4) is in accordance with TC retrieved from cooling curves of temperature-dependent magnetic susceptibility measurements (195–232 °C). However, thermomagnetic curves are irreversible either with lower (type I) or higher (type II) TC in the heating curve. All curves show transition temperatures above ca. 390 °C, indicating maghemitization. We interpret the irreversibility of TC (∆TC) in terms of different degrees of cation ordering, overprinted or masked by different degrees of maghemitization, which is a low-temperature phenomenon. Negative ∆TC indicates that original deposited titanomagnetite has cooled faster and, therefore, has stored a lower degree of cation ordering compared to heating/cooling rate of 11 °C/min in the Kappabridge. Type II with positive ∆TC indicates higher degree of cation ordering, and, therefore, slower cooling rate. The central part of this deposit shows most severe maghemitization, indicating rather wet emplacement. We, therefore, suggest different eruption styles for deposition of type I pyroclastics with more phreatomagmatic and type II pyroclastics with more phreato-Strombolian eruption styles. Our study is a new approach to discriminate different cooling histories in maar deposits using the Curie temperature of titanomagnetite. We suggest that this method has the potential to discriminate different emplacement modes resulting from different eruption styles. © 2020, The Author(s). Article 2020 English 14373254 10.1007/s00531-020-01865-1 International Journal of Earth Sciences 109 Springer 1707 – 1725 5 Czech Republic; cooling; emplacement; mineral alteration; Pleistocene; pyroclastic deposit; tephra; volcanic eruption https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084602885&doi=10.1007%2fs00531-020-01865-1&partnerID=40&md5=10681e60eb46f6b7fdac734d61a97678 Cited by: 6; All Open Access, Green Open Access, Hybrid Gold Open Access Philipp Lied Agnes Kontny Norbert Nowaczyk Jan Mrlina Horst Kämpf article Liu2020 The Hartoušov mofette system is a natural CO2 degassing site in the central Cheb Basin (Eger Rift, Central Europe). In early 2016 a 108 m deep core was obtained from this system to investigate the impact of ascending mantle-derived CO2 on indigenous deep microbial communities and their surrounding life habitat. During drilling, a CO2 blow out occurred at a depth of 78.5 meter below surface (mbs) suggesting a CO2 reservoir associated with a deep low-permeable CO2-saturated saline aquifer at the transition from Early Miocene terrestrial to lacustrine sediments. Past microbial communities were investigated by hopanoids and glycerol dialkyl glycerol tetraethers (GDGTs) reflecting the environmental conditions during the time of deposition rather than showing a signal of the current deep biosphere. The composition and distribution of the deep microbial community potentially stimulated by the upward migration of CO2 starting during Mid Pleistocene time was investigated by intact polar lipids (IPLs), quantitative polymerase chain reaction (qPCR), and deoxyribonucleic acid (DNA) analysis. The deep biosphere is characterized by microorganisms that are linked to the distribution and migration of the ascending CO2-saturated groundwater and the availability of organic matter instead of being linked to single lithological units of the investigated rock profile. Our findings revealed high relative abundances of common soil and water bacteria, in particular the facultative, anaerobic and potential iron-oxidizing Acidovorax and other members of the family Comamonadaceae across the whole recovered core. The results also highlighted the frequent detection of the putative sulfate-oxidizing and CO2-fixating genus Sulfuricurvum at certain depths. A set of new IPLs are suggested to be indicative for microorganisms associated to CO2 accumulation in the mofette system. © Copyright © 2020 Liu, Adler, Lipus, Kämpf, Bussert, Plessen, Schulz, Krauze, Horn, Wagner, Mangelsdorf and Alawi. Article 2020 English 1664302X 10.3389/fmicb.2020.543260 Frontiers in Microbiology 11 Frontiers Media S.A. biological marker; carbon; carbon dioxide; carbon nitrogen sulfur monocycle; clario star; fluorescein sodium; ground water; organic carbon; organic nitrogen; RNA 16S; soil organic matter; urea; Acidobacteria; Actinobacteria; Alphaproteobacteria; Arabidopsis thaliana; Article; bacterial microbiome; Bacteroidetes; Betaproteobacteria; biogeography; bioinformatics; biosphere; calibration; carbon dioxide fixing bacterium; Chloroflexi; column chromatography; Comamonadaceae; community structure; Crenarchaeota; cyanobacterium; DNA extraction; DNA purification; electrospray mass spectrometry; Escherichia coli; freeze drying; Gallionella; Gammaproteobacteria; gene sequence; geochemical analysis; high performance liquid chromatography; homogenate; isotope analysis; lipid analysis; liquid chromatography; methanogenesis; Methanosaeta; Methanosarcina; microbial biomass; microbial community; microbial contamination; microbial diversity; migration; Miocene; multidimensional scaling; nonhuman; organisms by metabolism; population abundance; real time polymerase chain reaction; saponification; soil microflora; stratigraphy; sulfate oxidizing bacterium; Sulfuricurvum; thermal spring; total nitrogen content; total organic carbon; ultra performance liquid chromatography https://www.scopus.com/inward/record.uri?eid=2-s2.0-85098243597&doi=10.3389%2ffmicb.2020.543260&partnerID=40&md5=f4ea3e97ac30c6c68bb32263cc60ba01 Cited by: 4; All Open Access, Gold Open Access, Green Open Access Qi Liu Karsten Adler Daniel Lipus Horst Kämpf Robert Bussert Birgit Plessen Hans-Martin Schulz Patryk Krauze Fabian Horn Dirk Wagner Kai Mangelsdorf Mashal Alawi article Fischer2020983 Monitoring of CO2 degassing in seismoactive areas allows the study of correlations of gas release and seismic activity. Reliable continuous monitoring of the gas flow rate in rough field conditions requires robust methods capable of measuring gas flow at different types of gas outlets such as wet mofettes, mineral springs, and boreholes. In this paper we focus on the methods and results of the long-term monitoring of CO2 degassing in the West Bohemia/Vogtland region in central Europe, which is typified by the occurrence of earthquake swarms and discharge of carbon dioxide of magmatic origin. Besides direct flow measurement using flowmeters, we introduce a novel indirect technique based on quantifying the gas bubble contents in a water column, which is capable of functioning in severe environmental conditions. The method calculates the mean bubble fraction in a water-gas mixture from the pressure difference along a fixed depth interval in a water column. Laboratory tests indicate the nonlinear dependence of the bubble fraction on the flow rate, which is confirmed by empirical models found in the chemical and nuclear engineering literature. Application of the method in a pilot borehole shows a high correlation between the bubble fraction and measured gas flow rate. This was specifically the case for two coseismic anomalies in 2008 and 2014, when the flow rate rose during a seismic swarm to a multitude of the preseismic level for several months and was followed by a long-term flow rate decline. However, three more seismic swarms occurring in the same fault zone were not associated with any significant CO2 flow anomaly.We surmise that this could be related to the slightly farther distance of the hypocenters of these swarms compared to the two ones which caused the coseismic CO2 flow rise. Further long-term CO2- flow monitoring is required to verify the mutual influence of CO2 degassing and seismic activity in the area. © 2020 Cambridge University Press. All rights reserved. Article 2020 English 18699510 10.5194/se-11-983-2020 Solid Earth 11 Copernicus GmbH 983 – 998 3 Bohemia; Czech Republic; Boreholes; Carbon dioxide; Degassing; Earthquakes; Flow measurement; Flow of gases; Gases; Mineral springs; Bubble fractions; Continuous monitoring; Earthquake swarms; Environmental conditions; Field conditions; Long term monitoring; Nonlinear dependence; Pressure differences; carbon dioxide; coseismic process; crustal structure; degassing; discharge; earthquake hypocenter; earthquake swarm; flow velocity; gas flow; monitoring; Flow rate https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086400975&doi=10.5194%2fse-11-983-2020&partnerID=40&md5=da43d9414beaa01569d3cda80dbc4adb Cited by: 6; All Open Access, Gold Open Access, Green Open Access Tomáš Fischer Josef Vlček Martin Lanzendörfer article Woith2020 Fluid anomalies were often considered as possible precursors before earthquakes. However, fluid properties at the surface can change for a variety of reasons, including environmental changes near the surface, the response of the superficial fluid system to loads associated with the mechanical nucleation of earthquake fractures, or as a result of transients in fluid flow from the depths. A key problem is to understand the origin of the anomaly and to distinguish between different causes. We present a new approach to monitor geochemical and geophysical fluid properties along a vertical profile in a set of drillings from a depth of a few hundred meters to the surface. This setup can provide hints on the origin of temporal variations, as the migration direction and speed of properties can be measured. In addition, potential admixtures of fluids from a deep crustal or mantle origin with meteoric fluids can be better quantified. A prototype of a multi-level gas monitoring system comprising flow and pressure probes, as well as monitoring of fluid-geochemical properties and stable isotopes is being implemented in a mofette field with massive CO2 (up to 97 tons per day) degassing. The mofette is believed a gas emission site where CO2 ascends through crustal-scale conduits from as deep as the upper mantle, and may therefore provide a natural window to ongoing magmatic processes at mantle depth. Fluids from three adjacent boreholes—30, 70, and 230 m deep—will be continuously monitored at high sampling rates. © Copyright © 2020 Woith, Daskalopoulou, Zimmer, Fischer, Vlček, Trubač, Rosberg, Vylita and Dahm. Article 2020 English 22966463 10.3389/feart.2020.585733 Frontiers in Earth Science 8 Frontiers Media S.A. Carbon dioxide; Earthquakes; Gas detectors; Geochemistry; Earthquake research; Environmental change; Gas monitoring systems; Geochemical properties; High sampling rates; Magmatic process; Temporal variation; Vertical profile; carbon dioxide; crustal structure; degassing; drilling; earthquake mechanism; earthquake swarm; fluid flow; fluid pressure; geochemistry; geophysics; hydrocarbon reservoir; monitoring; radon; Flow of fluids https://www.scopus.com/inward/record.uri?eid=2-s2.0-85095701694&doi=10.3389%2ffeart.2020.585733&partnerID=40&md5=4d18b65e05e23efba7c6dabf297cf33f Cited by: 4; All Open Access, Gold Open Access Heiko Woith Kyriaki Daskalopoulou Martin Zimmer Tomáš Fischer Josef Vlček Jakub Trubač Jan-Erik Rosberg Tomáš Vylita Torsten Dahm article Kämpf2019 This study presents the results of gas flux measurements of cold, mantle-derived CO2 release at the Bublák mofette field (BMF), located inside of the N-S directed Počátky Plesná fault zone (PPFZ). The PPFZ is presently seismically active, located in the eastern part of the Cheb Basin, western Eger Rift, Central Europe. The goal of the work was to identify the linkage between tectonics and gas flux. The investigated area has a size of 0,43 km2 in which 1.115 locations have been measured. Besides classical soil CO2 gas flux measurements using the closed chamber method (West Systems), drone-based orthophotos were used in combination with knowledge of plant zonation to find zones of high degassing in the agriculturally unused part of the BMF. The highest observed soil CO2 gas flux is 177.926,17 g m-2 d-1, and the lowest is 0,28 g m-2 d-1. Three statistical methods were used for the calculation of the gas flux: arithmetic mean, kriging, and trans-Gaussian kriging. The average CO2 soil degassing of the BMF is 30 t d-1 for an area of 0,43 km2. Since the CO2 soil degassing of the Hartoušov mofette field (HMF) amounts to 23 t d-1 for an area of 0,35 km2, the average dry degassing values of the BMF and HMF are in the same magnitude of order. The amount of CO2 flux from wet mofettes is 3 t d-1 for the BMF and 0,6 t d-1 for the HMF. It was found that the degassing in the BMF and HMF is not in accordance with the pull-apart basin interpretation, based on the direction of degassing as well as topography and sediment fill of the suggested basins. En-echelon faults inside of the PPFZ act as fluid channels to depth (CO2 conduits). These structures inside the PPFZ show beginning faulting and act as tectonic control of CO2 degassing. © 2019 Horst Kämpf et al. Article 2019 English 14688115 10.1155/2019/4852706 Geofluids 2019 Hindawi Limited Cheb Basin; Czech Republic; Karlovarsky; carbon dioxide; carbon emission; degassing; flux measurement; rift zone; tectonics https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075134293&doi=10.1155%2f2019%2f4852706&partnerID=40&md5=6494ee1b0111bb038a75e5c75126780e Cited by: 6; All Open Access, Gold Open Access, Green Open Access Horst Kämpf Alena Sophie Broge Pouria Marzban Masoud Allahbakhshi Tobias Nickschick article Nickschick20191951 <p>The Cheb Basin, a region of ongoing swarm earthquake activity in the western Czech Republic, is characterized by intense carbon dioxide degassing along two known fault zones - the N-S-striking Počatky-Plesná fault zone (PPZ) and the NW-SE-striking Mariánské Lázne fault zone (MLF). The fluid pathways for the ascending <span classCombining double low line"inline-formula">CO2</span> of mantle origin are one of the subjects of the International Continental Scientific Drilling Program (ICDP) project "Drilling the Eger Rift" in which several geophysical surveys are currently being carried out in this area to image the topmost hundreds of meters to assess the structural situation, as existing boreholes are not sufficiently deep to characterize it.</p> <p>As electrical resistivity is a sensitive parameter to the presence of conductive rock fractions as liquid fluids, clay minerals, and also metallic components, a large-scale dipole-dipole experiment using a special type of electric resistivity tomography (ERT) was carried out in June 2017 in order to image fluid-relevant structures. We used permanently placed data loggers for voltage measurements in conjunction with moving high-power current sources to generate sufficiently strong signals that could be detected all along the 6.5&thinsp;<span classCombining double low line"inline-formula">km</span> long profile with 100 and 150&thinsp;<span classCombining double low line"inline-formula">m</span> dipole spacings. After extensive processing of time series for voltage and current using a selective stacking approach, the pseudo-section is inverted, which results in a resistivity model that allows for reliable interpretations depths of up than 1000&thinsp;<span classCombining double low line"inline-formula">m</span>.</p> <p>The subsurface resistivity image reveals the deposition and transition of the overlying Neogene Vildštejn and Cypris formations, but it also shows a very conductive basement of phyllites and granites that can be attributed to high salinity or rock alteration by these fluids in the tectonically stressed basement. Distinct, narrow pathways for <span classCombining double low line"inline-formula">CO2</span> ascent are not observed with this kind of setup, which hints at wide degassing structures over several kilometers within the crust instead. We also observed gravity and GPS data along this profile in order to constrain ERT results. A gravity anomaly of ca. <span classCombining double low line"inline-formula">-9</span>&thinsp;<span classCombining double low line"inline-formula">mGal</span> marks the deepest part of the Cheb Basin where the ERT profile indicates a large accumulation of conductive rocks, indicating a very deep weathering or alteration of the phyllitic basement due to the ascent of magmatic fluids such as <span classCombining double low line"inline-formula">CO2</span>. We propose a conceptual model in which certain lithologic layers act as caps for the ascending fluids based on stratigraphic records and our results from this experiment, providing a basis for future drillings in the area aimed at studying and monitoring fluids.</p>. © Author(s) 2019. 2019 English 18699510 10.5194/se-10-1951-2019 Solid Earth 10 Copernicus GmbH 1951-1969 Institute for Geophysics and Geology, Leipzig University, Talstrasse 35, Leipzig, 04103, Germany; Leibniz Institute for Applied Geophysics, Stilleweg 2, Hanover, 30655, Germany; Institute of Geophysics CAS, Boční II 1401, Prague, 141 31, Czech Republic 6 Buildings; Carbon dioxide; Degassing; Drilling fluids; Electric conductivity; Geophysics; Global positioning system; Infill drilling; Stratigraphy; Weathering, Continental scientific drillings; Earthquake activity; Electric resistivity tomography; Electrical resistivity tomography; Geophysical surveys; Resistivity modeling; Sensitive parameter; Stratigraphic records, Electric lines, carbon dioxide; degassing; earthquake swarm; electrical resistivity; fault zone; monitoring; tomography, Cheb Basin; Czech Republic; Karlovarsky https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075055625&doi=10.5194%2fse-10-1951-2019&partnerID=40&md5=4b9a0e021e789ab0a50916d1fce58fa5 cited By 7 T. Nickschick C. Flechsig J. Mrlina F. Oppermann F. Löbig article Kriegerowski2019317 We develop an amplitude spectral ratio method for event couples from clustered earthquakes to estimate seismic wave attenuation (<span classCombining double low line"inline-formula"><i>Q</i>ĝ'1</span>) in the source volume. The method allows to study attenuation within the source region of earthquake swarms or aftershocks at depth, independent of wave path and attenuation between source region and surface station. We exploit the high-frequency slope of phase spectra using multitaper spectral estimates. The method is tested using simulated full wave-field seismograms affected by recorded noise and finite source rupture. The synthetic tests verify the approach and show that solutions are independent of focal mechanisms but also show that seismic noise may broaden the scatter of results. We apply the event couple spectral ratio method to northwest Bohemia, Czech Republic, a region characterized by the persistent occurrence of earthquake swarms in a confined source region at mid-crustal depth. Our method indicates a strong anomaly of high attenuation in the source region of the swarm with an averaged attenuation factor of <span classCombining double low line"inline-formula"><i>Q</i>p&lt;100</span>. The application to S phases fails due to scattered P-phase energy interfering with S phases. The <span classCombining double low line"inline-formula"><i>Q</i>p</span> anomaly supports the common hypothesis of highly fractured and fluid saturated rocks in the source region of the swarms in northwest Bohemia. However, high temperatures in a small volume around the swarms cannot be excluded to explain our observations. © 2019. This work is distributed under the Creative Commons Attribution 4.0 License. Article 2019 English 18699510 10.5194/se-10-317-2019 Solid Earth 10 Copernicus GmbH 317 – 328 1 Bohemia; Czech Republic; Transport properties; Amplitude spectral ratio; Attenuation factors; Earthquake swarms; High frequency HF; High temperature; Seismic wave attenuations; Spectral estimate; Spectral ratios; aftershock; earthquake swarm; seismic attenuation; seismic source; seismic wave; spectral analysis; Earthquake effects https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061316174&doi=10.5194%2fse-10-317-2019&partnerID=40&md5=fa53aaab622308e907582c603bbebdf8 Cited by: 6; All Open Access, Gold Open Access, Green Open Access Marius Kriegerowski Simone Cesca Matthias Ohrnberger Torsten Dahm Frank Kruger article Umlauft20191550 Presently ongoing geodynamic processes within the intracontinental lithospheric mantle give rise to different natural phenomena in the NW Bohemia/Vogtland region (Czech Republic, Germany), amongst others: earthquake swarms, mineral springs and degassing zones of mantle-derived fluids as well as highly concentrated CO2 (mofettes). Their interaction mechanisms and relations are not yet fully understood, but fluid pathways within the crust are assumed, that allow efficient fluid transport between the main hypocentral swarm quake region and the degassing areas at the surface. Here, we focus on the location of the presumed fluid channels as well as on the investigation of their near-surface spatio-temporal variability, targeting a depth of a few hundreds of metmetres. We applied a 3-D matched field processing (MFP) approach in the frequency band of 10?20 Hz considering the fluid flow as seismic noise source. Within three campaigns in 2015/2016, we recorded continuous seismic noise data on the Hartoušov Mofette Field within the Cheb Basin (NW Bohemia, CZ), which is a key site to study fluid flow as it is characterized by strong and continuous surface degassing of CO2.We used temporary arrays varying in extent (70-600 m aperture) and in the amount of stations (25?95 units). Assuming a homogeneous velocity model and applying conventional MFP phase-matching over a 3-D grid search, we located two channel-like structures beneath the test site, which could be traced down to a common source area down to 2000 m depth. We thereby evaluated the influence of amplitude normalization of the measured noise signal on the MFP location considering water-filled or dry mofette channels. Additionally, a spatiotemporal analysis using time windows with a length of 10 min during 5 hr of noise record shows variability of fluid flow activity in space and time and hence, its migration beneath the test site on a short timescale. © 2019. Published by Oxford University Press on behalf of The Royal Astronomical Society. Article 2019 English 0956540X 10.1093/gji/ggz385 Geophysical Journal International 219 Oxford University Press 1550 – 1561 3 Bohemia; Czech Republic; Germany; Vogtland; Degassing; Earthquakes; Flow of fluids; Location; Mineral springs; Numerical models; Phase matching; Time series analysis; Continuous surface; Geodynamic process; Interaction mechanisms; Lithospheric mantle; Matched field processing; Seismic noise; Spatiotemporal analysis; Spatiotemporal variability; carbon dioxide; degassing; earthquake hypocenter; earthquake swarm; flow field; fluid flow; geodynamics; lithospheric structure; mantle structure; numerical model; seismic migration; seismic noise; seismic velocity; spatiotemporal analysis; three-dimensional modeling; time series analysis; Transport properties https://www.scopus.com/inward/record.uri?eid=2-s2.0-85072770056&doi=10.1093%2fgji%2fggz385&partnerID=40&md5=b2db1f1f0eb6a71acc192e5b76866571 Cited by: 8 J. Umlauft M. Korn article Liu2018 The Cheb Basin (CZ) is a shallow Neogene intracontinental basin filled with fluvial and lacustrine sediments that is located in the western part of the Eger Rift. The basin is situated in a seismically active area and is characterized by diffuse degassing of mantle-derived CO2 in mofette fields. The Hartoušov mofette field shows a daily CO2 flux of 23-97 tons of CO2 released over an area of 0.35 km2 and a soil gas concentration of up to 100% CO2. The present study aims to explore the geo-bio interactions provoked by the influence of elevated CO2 concentrations on the geochemistry and microbial community of soils and sediments. To sample the strata, two 3-m cores were recovered. One core stems from the center of the degassing structure, whereas the other core was taken 8 m from the ENE and served as an undisturbed reference site. The sites were compared regarding their geochemical features, microbial abundances, and microbial community structures. The mofette site is characterized by a low pH and high TOC/sulfate contents. Striking differences in the microbial community highlight the substantial impact of elevated CO2 concentrations and their associated side effects on microbial processes. The abundance of microbes did not show a typical decrease with depth, indicating that the uprising CO2-rich fluid provides sufficient substrate for chemolithoautotrophic anaerobic microorganisms. Illumina MiSeq sequencing of the 16S rRNA genes and multivariate statistics reveals that the pH strongly influences microbial composition and explains around 38.7% of the variance at the mofette site and 22.4% of the variance between the mofette site and the undisturbed reference site. Accordingly, acidophilic microorganisms (e.g., OTUs assigned to Acidobacteriaceae and Acidithiobacillus) displayed a much higher relative abundance at the mofette site than at the reference site. The microbial community at the mofette site is characterized by a high relative abundance of methanogens and taxa involved in sulfur cycling. The present study provides intriguing insights into microbial life and geo-bio interactions in an active seismic region dominated by emanating mantle-derived CO2-rich fluids, and thereby builds the basis for further studies, e.g., focusing on the functional repertoire of the communities. However, it remains open if the observed patterns can be generalized for different time-points or sites. © 2018 Frontiers Media S.A. All Rights Reserved. Article 2018 English 1664302X 10.3389/fmicb.2018.02787 Frontiers in Microbiology 9 Frontiers Media S.A. NOV carbon dioxide; RNA 16S; Acidithiobacillus; amplicon; Article; bioinformatics; DNA extraction; DNA purification; dsrB gene; gasification; gene; gene amplification; geochemical analysis; microbial community; nonhuman; pH; population abundance; real time polymerase chain reaction; stratigraphy https://www.scopus.com/inward/record.uri?eid=2-s2.0-85057591088&doi=10.3389%2ffmicb.2018.02787&partnerID=40&md5=9c203f01ec923ff7eee0334137edc18b Cited by: 4; All Open Access, Gold Open Access, Green Open Access Qi Liu Horst Kämpf Robert Bussert Patryk Krauze Fabian Horn Tobias Nickschick Birgit Plessen Dirk Wagner Mashal Alawi article Bräuer2018131 We report new data of the regional distribution pattern of total gas compositions as well as He and CO2 isotopic compositions from 25 gas exhalations in the western Eger Rift and its surroundings. Additionally, the first time-series data from gas exhalations in a clay pit within the Cheb Basin (CB) are given. At 21 degassing locations, the first data were obtained >20 years ago. From 7 locations within the degassing center CB and from 3 degassing sites belonging to the Mariánské Lázně (ML) degassing center, neon and argon isotope compositions were determined also. CO2 is the major component at all degassing sites. The δ13C values display a small range (−1.7 to −5.1‰) and the 3He/4He ratios vary from 1.9 to 5.9 Ra. The highest 3He/4He ratios are found at locations along the Počatky-Plesná Fault Zone, followed by the degassing site in the clay pit on the Nová Ves Fault and the locations on the ML fault at the edge of the CB. Although gas flow and CO2 concentrations in all degassing centers are very high, the fractions of mantle-derived helium are different, with presently up to 94% (in relation to the SCLM 3He/4He of 6.32 Ra) in the CB, up to 73% in the ML and up to 35% in the Karlovy Vary degassing center. At the locations in the eastern part of the CB a clear, progressive increase of the 3He/4He ratio has been observed since the first sampling campaigns there in 1993 and 1994, whereas at the other degassing sites the helium isotope ratio remained essentially the same. The progressive increase of the 3He/4He ratio in the eastern part of the CB, together with further short-time increases up to 6.3 Ra at one location (Bublák) before both the 2000 and 2008 earthquake swarms, indicate an ongoing magmatic process beneath this area, which seems to be associated with the occurrence of seismicity. The CB is located close to the Nový Kostel focal zone where since the beginning of our investigations four strong periods of seismicity (with magnitudes >3) occurred. The latest gas data confirm our earlier findings: time-series studies showed that in relation with seismic events, decreased 3He/4He ratios were repeatedly observed due to admixed seismically released crustal helium. Presently, the eastern part of the CB is the most active non-volcanic region in the European Cenozoic Rift System, with gas signatures similar to those found in free mantle-derived gases from the East African Rift system. © 2018 Elsevier B.V. Article 2018 English 00092541 10.1016/j.chemgeo.2018.02.017 Chemical Geology 482 Elsevier B.V. 131 – 145 Cheb Basin; Czech Republic; Karlovarsky; Carbon; Carbon dioxide; Degassing; Flow of gases; Gases; Helium; Inert gases; Isotopes; Location; Seismology; Time series; Earthquake swarms; Eger Rift; Isotopic composition; Magmatic CO2; Regional distribution; Sampling campaigns; SCLM; ^3He/^4He ratios; carbon dioxide; carbon isotope; helium isotope; isotopic composition; isotopic ratio; magmatism; monitoring; noble gas; rift zone; seismicity; Earthquakes https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042048926&doi=10.1016%2fj.chemgeo.2018.02.017&partnerID=40&md5=c66091ee56dcfaabe987f88772ace1a3 Cited by: 19 Karin Bräuer Horst Kämpf Samuel Niedermann Gerhard Strauch article Rohrmüller20181381 After a comprehensive geophysical prospecting the Quaternary Mýtina Maar, located on a line between the two Quaternary scoria cones Komorní hůrka/Kammerbühl and Železná hůrka/Eisenbühl, could be revealed by a scientific drilling at the German–Czech border in 2007. Further geophysical field investigations led to the discovery of another geological structure about 2.5 km ESE of the small town Neualbenreuth (NE-Bavaria, Germany), inferred to be also a maar structure, being the fourth volcanic feature aligned along the NW–SE trending Tachov fault zone. It is only faintly indicated as a partial circular rim in the digital elevation model. Though not expressed by a clear magnetic anomaly, geoelectric and refraction seismic tomography strongly indicates a bowl-shaped depression filled with low-resistivity and low-velocity material, correlating well with the well-defined negative gravity anomaly of − 2.5 mGal. Below ca. 15 m-thick debris layer, successions of mostly laminated sediments were recovered in a 100 m-long sediment core in 2015. Sections of finely laminated layers, likely varves, rich in organic matter and tree pollen, were recognized in the upper (22–30 m) and lower (70–86 m) part of the core, respectively, interpreted as interglacials, whereas mostly minerogenic laminated deposits, poor in organic matter, and (almost) barren of tree pollen are interpreted as clastic glacial deposits. According to a preliminary age model based on magnetostratigraphy, palynology, radiocarbon dating, and cyclostratigraphy, the recovered sediments span the time window from about 85 ka back to about 270 ka, covering marine isotope stages 5–8. Sedimentation rates are in the range of 10 cm ka−1 in interglacials and up to 100 cm ka−1 in glacial phases. The stratigraphic record resembles the one from Mýtina Maar, with its eruption date being derived from a nearby tephra deposit at 288 ± 17 ka, thus supporting the age model of the inferred Neualbenreuth Maar. © 2017, Springer-Verlag GmbH Germany. Article 2018 English 14373254 10.1007/s00531-017-1543-0 International Journal of Earth Sciences 107 Springer Verlag 1381 – 1405 Bayerisches Landesamt für Umwelt/Bavarian Environment Agency, Leopoldstraße 30, Marktredwitz, 95615, Germany; GFZ German Research Centre for Geosciences, Section 3.2, Telegrafenberg, Potsdam, 14473, Germany; Bayerisches Landesamt für Umwelt/Bavarian Environment Agency, Haunstetter Straße 112, Augsburg, 86161, Germany; GFZ German Research Centre for Geosciences, Section 5.2, Telegrafenberg, Potsdam, 14473, Germany; Institute of Earth and Environmental Science, University of Potsdam, Potsdam, Germany; Institute of Geophysics CAS, Bocni II 1401, Praha 4, 141 31, Czech Republic; Senckenberg Research Station of Quaternary Palaeontology Weimar, Weimar, 99423, Germany; Institute of Geography and Geology, University of Greifswald, Greifswald, 17489, Germany 4 Bavaria; Bohemian Massif; Czech Republic; Eger; Germany; Heves; Hungary; digital elevation model; fault zone; geophysical method; maar; magnetostratigraphy; paleoclimate; palynology; Quaternary; radiocarbon dating; tephra; volcanism https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030854959&doi=10.1007%2fs00531-017-1543-0&partnerID=40&md5=786412ed77f31fe322053de74511e21e Cited by: 18 J. Rohrmüller H. Kämpf E. Geiß J. Großmann I. Grun J. Mingram J. Mrlina B. Plessen M. Stebich C. Veress A. Wendt N. Nowaczyk article Muñoz20181 The West Bohemia/Vogtland region, characterized by the intersection of the Eger (Ohře) Rift and the Mariánské Lázně fault, is a geodynamically active area exhibiting repeated occurrence of earthquake swarms, massive CO2 emanations and mid Pleistocene volcanism. The Eger Rift is the only known intra-continental region in Europe where such deep seated, active lithospheric processes currently take place. We present an image of electrical resistivity obtained from two-dimensional inversion of magnetotelluric (MT) data acquired along a regional profile crossing the Eger Rift. At the near surface, the Cheb basin and the aquifer feeding the mofette fields of Bublák and Hartoušov have been imaged as part of a region of very low resistivity. The most striking resistivity feature, however, is a deep reaching conductive channel which extends from the surface into the lower crust spatially correlated with the hypocentres of the seismic events of the Nový Kostel Focal Zone. This channel has been interpreted as imaging a pathway from a possible mid-crustal fluid reservoir to the surface. The resistivity model reinforces the relation between the fluid circulation along deep-reaching faults and the generation of the earthquakes. Additionally, a further conductive channel has been revealed to the south of the profile. This other feature could be associated to fossil hydrothermal alteration related to Mýtina and/or Neualbenreuth Maar structures or alternatively could be the signature of a structure associated to the suture between the Saxo-Thuringian and Teplá-Barrandian zones, whose surface expression is located only a few kilometres away. © 2018 Elsevier B.V. Article 2018 English 00401951 10.1016/j.tecto.2018.01.012 Tectonophysics 727 Elsevier B.V. 1 – 11 Bohemia; Czech Republic; Germany; Vogtland; Aquifers; Clay alteration; Faulting; Fluids; Magnetotellurics; Conductive channels; Earthquake swarms; Hydrothermal alterations; Lithospheric process; Resistivity modeling; Surface expression; Vogtland; West Bohemia; earthquake swarm; electrical resistivity; fault; hydrothermal alteration; lower crust; magnetotelluric method; Earthquakes https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044308798&doi=10.1016%2fj.tecto.2018.01.012&partnerID=40&md5=bb4963829596b2fa7887c45c697e0477 Cited by: 8 Gerard Muñoz Ute Weckmann Josef Pek Světlana Kováčiková Radek Klanica article Vavryčuk20173701 The occurrence and specific properties of earthquake swarms in geothermal areas are usually attributed to a highly fractured rock and/or heterogeneous stress within the rock mass being triggered by magmatic or hydrothermal fluid intrusion. The increase of fluid pressure destabilizes fractures and causes their opening and subsequent shear-tensile rupture. The spreading and evolution of the seismic activity are controlled by fluid flow due to diffusion in a permeable rock (fluid-diffusion model) and/or by redistribution of Coulomb stress (intrusion model). These models, however, are not valid universally. We provide evidence that none of these models is consistent with observations of swarm earthquakes in West Bohemia, Czech Republic. Full seismic moment tensors of microearthquakes in the 2008 swarm in West Bohemia indicate that fracturing at the starting phase of the swarm was not associated with fault openings caused by pressurized fluids but rather with fault compactions. This can physically be explained by a fault-weakening model, when the essential role in the swarm triggering is attributed to degradation of fault strength due to long-lasting chemical and hydrothermal fluid-rock interactions in the focal zone. Since the rock is exposed to circulating hydrothermal, CO2-saturated fluids, the walls of fractures are weakened by dissolving and altering various minerals. The porosity of the fault gauge increases, and the fault weakens. If fault strength lowers to a critical value, the seismicity is triggered. The fractures are compacted during failure, the fault strength recovers, and a new cycle begins. ©2017. American Geophysical Union. All Rights Reserved. Article 2017 English 21699313 10.1002/2017JB013958 Journal of Geophysical Research: Solid Earth 122 Blackwell Publishing Ltd 3701 – 3718 5 Bohemia; Czech Republic; earthquake swarm; erosion; fault; fluid pressure; hydrothermal fluid; intraplate process; microearthquake; moment tensor; seismology https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018379667&doi=10.1002%2f2017JB013958&partnerID=40&md5=bfd4a443930d10ddb23e55ffcf5e319b Cited by: 31; All Open Access, Hybrid Gold Open Access Václav Vavryčuk Pavla Hrubcová article Krauze2017 The Cheb Basin (NW Bohemia, Czech Republic) is a shallow, neogene intracontinental basin. It is a non-volcanic region which features frequent earthquake swarms and large-scale diffuse degassing of mantle-derived CO2 at the surface that occurs in the form of CO2-rich mineral springs and wet and dry mofettes. So far, the influence of CO2 degassing onto the microbial communities has been studied for soil environments, but not for aquatic systems. We hypothesized, that deep-trenching CO2 conduits interconnect the subsurface with the surface. This admixture of deep thermal fluids should be reflected in geochemical parameters and in the microbial community compositions. In the present study four mineral water springs and two wet mofettes were investigated through an interdisciplinary survey. The waters were acidic and differed in terms of organic carbon and anion/cation concentrations. Element geochemical and isotope analyses of fluid components were used to verify the origin of the fluids. Prokaryotic communities were characterized through quantitative PCR and Illumina 16S rRNA gene sequencing. Putative chemolithotrophic, anaerobic and microaerophilic organisms connected to sulfur (e.g., Sulfuricurvum, Sulfurimonas) and iron (e.g., Gallionella, Sideroxydans) cycling shaped the core community. Additionally, CO2-influenced waters form an ecosystem containing many taxa that are usually found in marine or terrestrial subsurface ecosystems. Multivariate statistics highlighted the influence of environmental parameters such as pH, Fe2+ concentration and conductivity on species distribution. The hydrochemical and microbiological survey introduces a new perspective on mofettes. Our results support that mofettes are either analogs or rather windows into the deep biosphere and furthermore enable access to deeply buried paleo-sediments. © 2017 Krauze, Kämpf, Horn, Liu, Voropaev, Wagner and Alawi. Article 2017 English 1664302X 10.3389/fmicb.2017.02446 Frontiers in Microbiology 8 Frontiers Media S.A. DEC carbon dioxide; helium; hydrogen; iron; mineral water; organic carbon; Actinobacteria; aquatic environment; Article; chromatography by stationary phase; controlled study; correlation analysis; Czech Republic; earthquake; electrical conductivity parameters; environmental factor; freshwater environment; geochemical analysis; hypoxia; isotope analysis; limit of quantitation; mass spectrometry; microbial community; microbiology; multivariate analysis; nonhuman; Proteobacteria; reverse transcription polymerase chain reaction; sequence analysis; soil analysis https://www.scopus.com/inward/record.uri?eid=2-s2.0-85037736645&doi=10.3389%2ffmicb.2017.02446&partnerID=40&md5=1f1be753f5037ec265557da76df0765f Cited by: 17; All Open Access, Gold Open Access, Green Open Access Patryk Krauze Horst Kämpf Fabian Horn Qi Liu Andrey Voropaev Dirk Wagner Mashal Alawi article Fischer201760 The West Bohemia/Vogtland region is characterized by earthquake swarm activity and degassing of CO2 of mantle origin. A fast increase of CO2 flow rate was observed 4 days after a ML 3.5 earthquake in May 2014 in the Hartoušov mofette, 9 km from the epicentres. During the subsequent 150 days the flow reached sixfold of the original level, and has been slowly decaying until present. Similar behavior was observed during and after the swarm in 2008 pointing to a fault-valve mechanism in long-term. Here, we present the results of simulation of gas flow in a two dimensional model of Earth's crust composed of a sealing layer at the hypocentre depth which is penetrated by the earthquake fault and releases fluid from a relatively low-permeability lower crust. This simple model is capable of explaining the observations, including the short travel time of the flow pulse from 8 km depth to the surface, long-term flow increase and its subsequent slow decay. Our model is consistent with other analyse of the 2014 aftershocks which attributes their anomalous character to exponentially decreasing external fluid force. Our observations and model hence track the fluid pressure pulse from depth where it was responsible for aftershocks triggering to the surface where a significant long-term increase of CO2 flow started 4 days later. © 2016 Elsevier B.V. Article 2017 English 0012821X 10.1016/j.epsl.2016.12.001 Earth and Planetary Science Letters 460 Elsevier B.V. 60 – 67 Bohemia; Czech Republic; Germany; Vogtland; Carbon dioxide; Faulting; Flow of gases; Structural geology; crustal CO2; Earthquake fault; Earthquake swarms; Enhanced permeability; Fault-valve; Fluid pressure pulse; Low permeability; Two dimensional model; carbon dioxide; degassing; earthquake epicenter; earthquake magnitude; earthquake mechanism; earthquake swarm; lower crust; permeability; trigger mechanism; Earthquakes https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006921244&doi=10.1016%2fj.epsl.2016.12.001&partnerID=40&md5=7ae0105dadfa0b007dabd88d5f073f42 Cited by: 39 T. Fischer C. Matyska J. Heinicke article Kind201719 We used S-receiver functions (i.e. S-to-P converted signals) to study seismic discontinuities in the upper mantle between the Moho and the 410 km discontinuity beneath central Europe. This was done by using c. 49,000 S-receiver functions from c. 700 permanent and temporary broadband stations made available by the open EIDA Archives. Below Phanerozoic Europe we observed expected discontinuities like the Moho, the lithosphere-asthenosphere boundary (LAB), the Lehmann discontinuity and the 410 km discontinuity with an additional overlying low velocity zone. Below the East European Craton (EEC), we observed the Mid-Lithospheric Discontinuity (MLD) at c. 100 km depth as well as the controversial cratonic LAB at c. 200 km depth. At the boundary of the EEC but still below the Phanerozoic surface, we observed downward velocity reductions below the LAB in the following regions: the North German-Polish Plain at about 200 km depth; the Bohemian Massive, north-west dipping from 200 to 300 km depth; the Pannonian Basin, north-east dipping from 150 to 200 km depth underneath the western Carpathians and the EEC. We named this newly observed structure Sub-Lithospheric Discontinuity (SLD). At the northern edge of the Bohemian Massive, we see a sharp vertical step of about 100 km between the SLD below the Bohemian Massive and the North German-Polish Plain. This step follows the surface trace of the Rheic Suture between the continental Saxo-Thuringian and Rheno-Herzynian zones of the Variscan orogen. A preliminary interpretation of these features is that a prong of the cratonic mantle lithosphere penetrated the Phanerozoic asthenosphere during the continental collision at the western and south-western edges of the EEC. © 2017 Elsevier B.V. Article 2017 English 00401951 10.1016/j.tecto.2017.02.002 Tectonophysics 700-701 Elsevier B.V. 19 – 31 Bohemian Massif; East European Craton; Pannonian Basin; Laboratories; Bohemian massifs; East-European craton; Lithosphere-asthenosphere boundary; Lithospheric; Pannonian basin; S-receiver functions; asthenosphere; craton; discontinuity; lithosphere; Moho; seismograph; upper mantle; Structural geology https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013127722&doi=10.1016%2fj.tecto.2017.02.002&partnerID=40&md5=d96198b0cacdf922cdd3f2ed5a420b9c Cited by: 17 Rainer Kind Mark R. Handy Xiaohui Yuan Thomas Meier Horst Kämpf Riaz Soomro article Bussert201713 Microbial life in the continental "deep biosphere" is closely linked to geodynamic processes, yet this interaction is poorly studied. The Cheb Basin in the western Eger Rift (Czech Republic) is an ideal place for such a study because it displays almost permanent seismic activity along active faults with earthquake swarms up to ML 4.5 and intense degassing of mantle-derived CO2 in conduits that show up at the surface in form of mofettes. We hypothesize that microbial life is significantly accelerated in active fault zones and in CO2 conduits, due to increased fluid and substrate flow. To test this hypothesis, pilot hole HJB-1 was drilled in spring 2016 at the major mofette of the Hartoušov mofette field, after extensive pre-drill surveys to optimize the well location. After drilling through a thin caprock-like structure at 78.5 m, a CO2 blowout occurred indicating a CO2 reservoir in the underlying sandy clay. A pumping test revealed the presence of mineral water dominated by Na+, Ca2+, HCO3-, SO42- (Na-Ca-HCO3-SO4 type) having a temperature of 18.6 °C and a conductivity of 6760 μScm-1. The high content of sulfate (1470 mg L-1) is typical of Carlsbad Spa mineral waters. The hole penetrated about 90 m of Cenozoic sediments and reached a final depth of 108.50m in Palaeozoic schists. Core recovery was about 85 %. The cored sediments are mudstones with minor carbonates, sandstones and lignite coals that were deposited in a lacustrine environment. Deformation structures and alteration features are abundant in the core. Ongoing studies will show if they result from the flow of CO2-rich fluids or not. © Author(s) 2017. 2017 English 18168957 10.5194/sd-23-13-2017 Scientific Drilling 23 Copernicus GmbH 13-27 Institute of Applied Geosciences, Technische Universität Berlin, Berlin, 13355, Germany; GFZ German Research Centre for Geosciences, Section 3.2: Organic Geochemistry, Potsdam, 14473, Germany; Institute for Geophysics and Geology, University of Leipzig, Leipzig, 04103, Germany; Leibniz Institute for Applied Geophysics, Hannover, 30655, Germany; GFZ German Research Centre for Geosciences, Section 5.3: Geomicrobiology, Potsdam, 14473, Germany; Balneological Institute, Karlovy Vary, 360 01, Czech Republic Beverages; Calcium; Carbon dioxide; Drilling fluids; Earthquakes; Faulting; Geodynamics; Reservoirs (water); Sodium; Sodium compounds; Sulfur compounds; Water, Cenozoic sediments; Czech Republic; Deformation structure; Earthquake swarms; Geodynamic process; Microbial life; Seismic activity; Well location, Calcium compounds https://www.scopus.com/inward/record.uri?eid=2-s2.0-85036612565&doi=10.5194%2fsd-23-13-2017&partnerID=40&md5=3e475b2abf298cd02f5860e8748eb64e cited By 16 R. Bussert H. Kämpf C. Flechsig K. Hesse T. Nickschick Q. Liu J. Umlauft T. Vylita D. Wagner T. Wonik H.E. Flores M. Alawi article Mousavi201764 We present a three-dimensional (3-D) P-wave attenuation (Qp) model for the geodynamically active swarm earthquake area of West Bohemia/Vogtland in the Czech/German border region. Path-averaged attenuation t* is calculated from amplitude spectra of time windows around the P-wave arrivals of local earthquakes. Average t/t* value or Qp for stations close to Nový Kostel are very low (< 150) compared to that of stations located further away from the focal zone (increases up to 500 within 80 km distance). The SIMUL2000 tomography scheme is used to invert the t* for P-wave attenuation perturbation. Analysis of resolution shows that our model is well-resolved in the vicinity of earthquake swarm hypocenters. The prominent features of the model are located around Nový Kostel focal zone and its northern vicinity. Beneath Nový Kostel a vertically stretched (down to depth of 11 km) and a highly attenuating body is observed. We believe that this is due to fracturing and high density of cracks inside the weak earthquake swarm zone in conjunction with presence of free gas/fluid. Further north of Nový Kostel two highly attenuating bodies are imaged which could represent fluid channels toward the surface. The eastern anomaly shows a good correlation with the fluid accumulation area which was suggested in 9HR seismic profile. © 2016 Elsevier B.V. 2017 English 00401951 10.1016/j.tecto.2016.12.010 Tectonophysics 695 Elsevier B.V. 64-75 Institute of Geophysics and Geology, University of Leipzig, Talstr. 35, Leipzig, D-4103, Germany; GFZ German Research Centre for Geosciences, Telegrafenberg, Potsdam, D-14473, Germany; Research School of Earth Sciences, Australian National University, Canberra, 2601, Australia Seismic waves, Body waves; Earthquake swarms; Europe; Seismic attenuation; Seismic tomography, Earthquakes, amplitude; body wave; earthquake hypocenter; earthquake swarm; P-wave; seismic attenuation; seismic tomography; seismicity; structural geology, Bohemia; Czech Republic; Germany; Vogtland https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006172660&doi=10.1016%2fj.tecto.2016.12.010&partnerID=40&md5=9f1730f6627f01f2df7f18546df9aceb cited By 13 S. Mousavi C. Haberland B. Hejrani M. Korn article Nickschick20172915 The Hartoušov mofette field in NW Bohemia, Czech Republic, is characterized by strong CO2 degassing from the Lithospheric Mantle. In a test survey using electrical resistivity tomography, we observed changes over time in the subsurface structure beneath heavily CO2 degassing spots to depths of about 40 m and compared them to CO2 gas flux and soil gas mappings from previous studies. Changes in the electrical resistivity were measured between September 2012 and October 2013 at irregular intervals and highlight large variations in the resistivity distribution where the CO2 degassing was strongest (56 × 103 g m−2 day−1), indicating a fluid-induced change of properties of the underlying clayey sediments. Positive and negative anomalies in the electric self-potential parallel to the ERTs can be found where CO2 degassing occurs which indicates varying ascent or descent of fluids within these spots. Some degassing spots seem not to be actively degassing continuously over time, which can also be observed by other studies in the same area. We suggest that future gas mappings are accompanied by methods that observe the state of fluid systems at subsurface over time, e.g. electric resistivity tomography and self potential. © 2017, Springer-Verlag Berlin Heidelberg. 2017 English 14373254 10.1007/s00531-017-1470-0 International Journal of Earth Sciences 106 Springer Verlag 2915-2926 Institute for Geophysics and Geology, University of Leipzig, Talstrasse 35, Leipzig, 04103, Germany; German Research Centre for Geosciences GFZ Potsdam, Section 4.3 Telegrafenberg, Potsdam, 14473, Germany; Institute of Geophysics, Academy of Sciences of the Czech Republic, Bocˇní II, Praha 4, 141 31, Czech Republic 8 carbon dioxide; carbon flux; degassing; electrical resistivity; fumarole; mantle structure; mapping; temporal variation; tomography, Bohemia; Cheb Basin; Czech Republic; Karlovarsky https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016045453&doi=10.1007%2fs00531-017-1470-0&partnerID=40&md5=acd19025974be7143993fda13e486fa9 cited By 6 T. Nickschick C. Flechsig C. Meinel J. Mrlina H. Kämpf article Hrubcová20172846 The Eger Rift is an active element of the European Cenozoic Rift System associated with intense Cenozoic intraplate alkaline volcanism and system of sedimentary basins. The intracontinental Cheb Basin at its western part displays geodynamic activity with fluid emanations, persistent seismicity, Cenozoic volcanism, and neotectonic crustal movements at the intersections of major intraplate faults. In this paper, we study detailed geometry of the crust/mantle boundary and its possible origin in the western Eger Rift. We review existing seismic and seismological studies, provide new interpretation of the reflection profile 9HR, and supplement it by new results from local seismicity. We identify significant lateral variations of the high-velocity lower crust and relate them to the distribution and chemical status of mantle-derived fluids and to xenolith studies from corresponding depths. New interpretation based on combined seismic and isotope study points to a local-scale magmatic emplacement at the base of the continental crust within a new rift environment. This concept of magmatic underplating is supported by detecting two types of the lower crust: a high-velocity lower crust with pronounced reflectivity and a high-velocity reflection-free lower crust. The character of the underplated material enables to differentiate timing and tectonic setting of two episodes with different times of origin of underplating events. The lower crust with high reflectivity evidences magmatic underplating west of the Eger Rift of the Late Variscan age. The reflection-free lower crust together with a strong reflector at its top at depths of ~28–30 km forms a magma body indicating magmatic underplating of the late Cenozoic (middle and upper Miocene) to recent. Spatial and temporal relations to recent geodynamic processes suggest active magmatic underplating in the intracontinental setting. ©2017. American Geophysical Union. All Rights Reserved. Article 2017 English 02787407 10.1002/2017TC004710 Tectonics 36 Blackwell Publishing Ltd 2846 – 2862 12 Eger; Heves; Hungary; Alkalinity; Reflection; Seismology; Velocity; Alkaline volcanism; Continental crusts; Eger Rift; Geodynamic process; Lateral variations; Lower crust; Magma bodies; Underplating; crust-mantle boundary; crustal movement; geodynamics; intraplate process; magmatic differentiation; rift zone; seismic reflection; underplating; Geodynamics https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040814317&doi=10.1002%2f2017TC004710&partnerID=40&md5=370c3f891f5e385841d66a0772395b7e Cited by: 21; All Open Access, Green Open Access Pavla Hrubcová Wolfram H. Geissler Karin Bräuer Václav Vavryčuk Čestmír Tomek Horst Kämpf article Hainzl20162575 The West Bohemia/Vogtland region, central Europe, is well known for its repeating swarm activity. However, the latest activity in 2014, although spatially overlapping with previous swarm activity, consisted of three classical aftershock sequences triggered by ML3.5, 4.4, and 3.5 events. To decode the apparent system change from swarm-type to mainshock-aftershock characteristics, we have analyzed the details of the major ML4.4 sequence based on focal mechanisms and relocated earthquake data. Our analysis shows that the mainshock occurred with rotated mechanism in a step over region of the fault plane, unfavorably oriented to the regional stress field. Most of its intense aftershock activity occurred in-plane with classical characteristics such as (i) the maximum magnitude of the aftershocks is significantly less than the mainshock magnitude and (ii) the decay can be well fitted by the Omori-Utsu law. However, the absolute number of aftershocks and the fitted Omori-Utsu c and p parameters are much larger than for typical sequences. By means of the epidemic-type aftershock sequence model, we show that an additional aseismic source with an exponentially decaying strength triggered a large fraction of the aftershocks. Corresponding pore pressure simulations with an exponentially decreasing flow rate of the fluid source show a good agreement with the observed spatial migration front of the aftershocks extending approximately with log(t). Thus, we conclude that the mainshock opened fluid pathways from a finite fluid source into the fault plane explaining the unusual high rate of aftershocks, the migration patterns, and the exponential decrease of the aseismic signal. ©2016. American Geophysical Union. All Rights Reserved. Article 2016 English 21699313 10.1002/2015JB012582 Journal of Geophysical Research: Solid Earth 121 Blackwell Publishing Ltd 2575 – 2590 4 Bohemia; Czech Republic; Germany; Vogtland; aftershock; earthquake magnitude; earthquake swarm; fault plane; focal mechanism; stress field https://www.scopus.com/inward/record.uri?eid=2-s2.0-84963647496&doi=10.1002%2f2015JB012582&partnerID=40&md5=85b48ca52c4eb8069206deca2a37ba3d Cited by: 41; All Open Access, Green Open Access S. Hainzl T. Fischer H. Čermáková M. Bachura J. Vlček article Schuessler20168548 We investigated the iron isotope signatures of dissolved Fe in the water of the Wettinquelle mineral spring (Bad Brambach, Germany) by time series sampling covering seismically active periods related to tectonic activity near the Eger Rift system in central Europe. Our objective was to test whether Fe isotopes trace earthquake-induced abiotic and biotic changes in the fluid/rock interaction of the deep, fissured, granitic aquifer. We found that the dissolved Fe isotope signatures in spring water are distinct from the granitic source signature (δ56Fe = +0.09‰). Particularly, we discovered that water δ56Fe values are remarkably stable (−0.01 ± 0.11‰, 2SD, n = 4) before and during a strong seismic swarm period in 2000 (local magnitudes ML > 3), while O2 and H2 concentrations in water decrease and dissolved Fe content increases. Later, recurring events of lower δ56Fe values down to −0.3‰ are observed in the period from 2001 to 2003 with intermittent seismic events (1 < ML < 3.2). The observations indicate a time lag between tectonic forcing and Fe isotope response. The role of abiotic fluid/rock interaction and Fe-utilizing bacteria identified in the mineral spring water on Fe isotope fractionation is discussed. We explain recurring changes toward isotopically lighter values by a combination of Fe dissolution from deep granite and admixture of isotopically light Fe generated by a complex combination of abiotic and biotic processes operating in the aquifer when disturbed by swarm earthquakes events. We propose a conceptual model scenario of earthquake-triggered changes in biogeochemical processes. ©2016. American Geophysical Union. All Rights Reserved. Article 2016 English 21699313 10.1002/2016JB013408 Journal of Geophysical Research: Solid Earth 121 Blackwell Publishing Ltd 8548 – 8568 12 Central Europe; Germany; aquifer; biochemistry; earthquake swarm; iron; isotopic fractionation; spring water; time series analysis https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007035459&doi=10.1002%2f2016JB013408&partnerID=40&md5=4a38cb44ef09e58937003e146505e833 Cited by: 29; All Open Access, Bronze Open Access, Green Open Access Jan A. Schuessler Horst Kämpf Ulrich Koch Mashal Alawi article Estrella2016327 The NW Bohemia/Vogtland region is characterized by currently ongoing geodynamic processes within the intracontinental lithospheric mantle. Among others, this activity results in the occurrence of mid-crustal earthquake swarms and CO2 degassing zones called mofettes. These two natural phenomena are related to each other since it is considered that fluid flow and fluid-induced effective stress can trigger earthquake swarms. At the Earth's surface, they appear spatially separated, but their connection could be explained by the existence of pathways within the crust that allow efficient and permanent fluid transport. However, neither the structure nor the position of such pathways has been imaged yet. With this background, we used a matched field processing analysis within the NW Bohemia/Vogtland region to locate mofettes and investigate their characteristics. Considering the CO2 degassing process as a high-frequency noise source, we chose two different test sites: the Dolní Částkov Borehole, which is an artificial mofette that we used to validate the method, and the South Hartoušov mofette field, a natural CO2 degassing area. On both sites, we measured seismic noise in a continuous mode for several hours (7 hours to 9 hours), with a sampling frequency of 250 samples/second, in multiple campaigns using an array of about 60 × 60 m2 with approximately 30 randomly distributed stations. For the matched field processing computation, the phase velocity c(□) of the study area is required, which we obtained from active seismic experiments with vertical hammer-blow as the source. The phase velocity varies between 200 m/s and 420 m/s for Dolní Částkov and between 100 m/s and 280 m/s for South Hartoušov, both in a frequency range of 7 Hz-60 Hz. With the matched field processing analysis at the artificial mofette in Dolní Částkov, we could relocate the noise source successfully. In the South Hartoušov mofette field, we detected one dominant vertically extended noise source, probably a fluid pathway, as well as a small matched field processing maxima at the surface that can be related to a dry mofette. © 2016 European Association of Geoscientists & Engineers. Article 2016 English 15694445 10.3997/1873-0604.2016024 Near Surface Geophysics 14 EAGE Publishing BV 327 – 335 4 Bohemia; Czech Republic; Germany; Vogtland; array; borehole; degassing; earthquake event; earthquake swarm; effective stress; fluid flow; phase velocity; seismic noise https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020474020&doi=10.3997%2f1873-0604.2016024&partnerID=40&md5=db6a8a6d0da7c9ce55df87b9778602c7 Cited by: 9 Hortencia Flores Estrella Josefine Umlauft Andreas Schmidt Michael Korn article Hrubcová2016881 The waveforms of microearthquakes are of high frequency and complicated. They contain many phases secondarily generated at crustal interfaces and at small-scale inhomogeneities. They are highly sensitive to focal mechanisms and thus very different for each station of local networks. However, with a large number of microearthquakes, the scattered waves present in the waveforms can serve for identifying the prominent crustal discontinuities and for determining their depth. In this paper, we develop a new approach for extracting information on crustal structure from such waveforms and apply it for determining depth and lateral variations of crustal discontinuities. We show that strong dependence of microseismic waveforms on radiation pattern requires good station coverage and knowledge of focal mechanisms of the microearthquakes. Analysis of real observations is supported by waveform modeling and by analysis of radiation patterns of scattered waves. The robustness of the inversion for depth of crustal interfaces is achieved by stacking of a large number of waveforms and by applying a grid search algorithm. The method is demonstrated on two microseismic data sets of different origin: microseismicity induced during the Continental Super-Deep Drilling Project (KTB) 2000 fluid injection experiment and natural seismicity in the West Bohemia swarm region. High-frequency conversions at the KTB site indicate a prominent interface at depths of 2.3-4.1 km consistent with previous interpretations. Geologically, it may represent the contact of granitoids with much faster metabasites underneath. Seismicity in West Bohemia indicates a strong-contrast interface at depths of 3.5-6.0 km. This interface is in agreement with previous profiling and might be related to trapping of fluid emanations ascending from the mantle. ©2016. American Geophysical Union. All Rights Reserved. Article 2016 English 21699313 10.1002/2015JB012548 Journal of Geophysical Research: Solid Earth 121 Blackwell Publishing Ltd 881 – 902 2 Bohemian Massif; crustal structure; discontinuity; earthquake swarm; focal mechanism; microearthquake; seismic wave; waveform analysis https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959420235&doi=10.1002%2f2015JB012548&partnerID=40&md5=391354c786c8354e37f6d0bebf5c3f43 Cited by: 11; All Open Access, Green Open Access, Hybrid Gold Open Access Pavla Hrubcová Václav Vavryčuk Alena Boušková Marco Bohnhoff article Mullick2015105 The western Eger rift at the Czech-German border in central Europe is an important geodynamically active area within the European Cenzoic rift system (ECRS) in the forelands of the Alps. Along with two other active areas of the ECRS, the French Massif Central and the east and west Eifel volcanic fields, it is characterized by numerous CO2-rich fluid emission points and frequent micro-seismicity. Existence of a plume(s) is indicated in the upper mantle which may be responsible for these observations. Here we reprocess a pre-existing deep seismic reflection profile '9HR' and interpret the subsurface structures as mapped by seismic reflectivity with previous findings, mainly from seismological and geochemical studies, to investigate the geodynamic activity in the subsurface. We find prominent hints of pathways which may allow magmatic fluids originating in the upper mantle to rise through the crust and cause the observed fluid emanations and earthquake activity. © 2015 Elsevier B.V. Article 2015 English 00401951 10.1016/j.tecto.2015.02.010 Tectonophysics 647 Elsevier B.V. 105 – 111 Alps; Bohemian Massif; Eger; Eifel; France; Germany; Heves; Hungary; Massif Central; Rhineland-Palatinate; Earthquakes; Bohemian massifs; Crustal fluids; Deep seismic reflection profiles; Earthquake activity; Eger rift; Rift systems; Seismic reflectivity; Subsurface structures; Cenozoic; earthquake swarm; geodynamics; rift zone; seismic reflection; seismicity; seismology; upper mantle; Geodynamics https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925966301&doi=10.1016%2fj.tecto.2015.02.010&partnerID=40&md5=215c26146a16ea6ed3b7716d39c29287 Cited by: 11 N. Mullick S. Buske P. Hrubcová B. Ruzek S. Shapiro P. Wigger T. Fischer article Mousavi20151113 The region of West Bohemia/Vogtland in the Czech-German border area is well known for the repeated occurrence of earthquake swarms, CO2 emanations and mofette fields. We present a local earthquake tomography study undertaken to image the Vp and Vp/Vs structure in the broader area of earthquake swarm activity. In comparison with previous investigations, more details of the near-surface geology, potential fluid pathways and features around and below the swarm focal zone could be revealed. In the uppermost crust, for the first time the Cheb basin and the Bublák/Hartoušov mofette fields were imaged as distinct anomalies of Vp and Vp/Vs. The well-pronounced low-Vp anomaly of the Cheb basin is not continuing into the Eger rift indicating a particular role of the basin within the rift system. A steep channel of increased Vp/Vs is interpreted as the pathway for fluids ascending from the earthquake swarm focal zone up to the Bublák/Hartoušov mofette fields. As a new feature, a mid-crustal body of high Vp and increased Vp/Vs is revealed just below and north of the earthquake swarm focal zone. It may represent a solidified intrusive body which emplaced prior or during the formation of the rift system. We speculate that enhanced fluid flow into the focal zone and triggering of earthquakes could be driven by the presence of the intrusive body if cooling is not fully completed. We consider the assumed intrusive structure as a heterogeneity leading to higher stress particularly at the junction of the rift system with the basin and prominent fault structures. This may additionally contribute to the triggering of earthquakes. © The Authors 2015. Article 2015 English 0956540X 10.1093/gji/ggv338 Geophysical Journal International 203 Oxford University Press 1113 – 1127 2 Germany; Vogtland; Flow of fluids; Seismographs; Body waves; Earthquake swarms; Europe; Fault structure; Fluid pathways; Near-surface geology; Seismic tomography; Seismicity and tectonics; body wave; earthquake swarm; seismic tomography; seismic velocity; seismicity; tectonics; Earthquakes https://www.scopus.com/inward/record.uri?eid=2-s2.0-84966711865&doi=10.1093%2fgji%2fggv338&partnerID=40&md5=37cf0b6092b42b1bacb3080fb8460cb7 Cited by: 20; All Open Access, Bronze Open Access, Green Open Access Sima Mousavi Klaus Bauer Michael Korn Babak Hejrani article Flechsig20152087 The Mýtina maar is the first known Quaternary maar in the Bohemian Massif. Based on the results of Mrlina et al. (J Volcanol Geother Res 182:97–112, 2009), a multiparametric geophysical (electrical resistivity tomography, gravimetry, magnetometry, seismics) and geological/petrochemical research study had been carried out. The interpretation of the data has provided new information about the inner structure of the volcanic complex: (1) specification of the depth of post-volcanic sedimentary fill (up to ~100 m) and (2) magnetic and resistivity signs of one (or two) hidden volcanic structures interpreted as intrusions or remains of a scoria cone. The findings at the outer structure of the maar incorporate the (1) evidence of circular fracture zones outside the maar, (2) detection and distribution of volcanic ejecta and tephra-fall deposits at the surface, and (3) indications from electrical resistivity tomography and gravity data in the area between the Mýtina maar and Železná hůrka scoria cone, interpreted as a palaeovalley, filled by volcaniclastic rocks, and aligned along the strike line (NW–SE) of the Tachov fault zone. These findings are valuable contributions to extend the knowledge about structure of maar volcanoes in general. Because of ongoing active magmatic processes in the north-east part of the Cheb Basin (ca. 15–30 km north of the investigation area), the Mýtina maar-diatreme volcano and surroundings is a suitable key area for research directed to reconstruction of the palaeovolcanic evolution and assessment of possible future hazard potential in the Bohemian Massif. © 2015, Springer-Verlag Berlin Heidelberg. Article 2015 English 14373254 10.1007/s00531-014-1136-0 International Journal of Earth Sciences 104 Springer Verlag 2087 – 2105 8 Bohemian Massif; Cheb Basin; Czech Republic; Karlovarsky; geological survey; geophysical survey; maar; Quaternary; reconstruction; volcanism https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945491128&doi=10.1007%2fs00531-014-1136-0&partnerID=40&md5=c60ec72595e852f74ae274b3647d07f8 Cited by: 17 Christina Flechsig Jens Heinicke Jan Mrlina Horst Kämpf Tobias Nickschick Alina Schmidt Tomáš Bayer Thomas Günther Carsten Rücker Elisabeth Seidel Michal Seidl article Kämpf20151909 Editorial 2015 English 14373254 10.1007/s00531-015-1252-5 International Journal of Earth Sciences 104 Springer Verlag 1909 – 1912 8 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945468911&doi=10.1007%2fs00531-015-1252-5&partnerID=40&md5=4a86ff2b0160647dc0b12f677301c522 Cited by: 0; All Open Access, Bronze Open Access Horst Kämpf Karoly Németh Jacek Puziewicz Jan Mrlina Wolfram H. Geissler article Nickschick20152107 Strong, subcontinental mantle-dominated CO2 degassing occurs in the Hartoušov and Bublák mofette fields in the western Eger Rift. The combination of CO2 gas flux and soil gas measurements as well as gravity and geoelectric surveys provides insight into the surface and subsurface of this unique mofette area. CO2 soil gas and gas flux measurements reveal that large amounts of carbon dioxide are released via channels with diameters below 1 m. Carbon dioxide emissions of several tens and up to more than 100 kg day−1 are ejected via these small seeps. Measurements with small spacings are necessary to account for the point like, focused gas discharge in the lesser degassing surrounding. We estimate that between 23 and 97 tons of CO2 are released over an area of about 350,000 m2 each day in the Hartoušov mofette field. The application of widely used geostatistical tools leads to estimations of the CO2 discharge with very high standard deviations due to the strong positive skewness of the data distribution. Geophysical investigations via electrical resistivity tomography and gravity measurements were carried out over areas of strong seepage and reveal distinct anomalies in the subsurface below mofettes, indicating rock and sediment alterations and/or sediment transport by pressurised, ascending CO2 and water mobilised by it. This study reveals that the gas emanations only occur west of a morphological step which is related to a N–S-oriented fault zone, the Počatky-Plesná fault zone. The results of CO2 mapping and the geophysical studies can track the course of this fault zone in this area. Our results fit into a tectonic model in which the mofette fields are in the centres of two independent pull-apart basin-like structures. We hypothesise that the sinistral strike-slip movement of the Počatky-Plesná fault zone leads to a pull-apart basin-like opening, at which the strong, mantle-derived CO2 degassing occurs nowadays. Since the Hartoušov and Bublák mofette fields only illustrate examples along the N–S-striking Počatky-Plesná fault zone, its role and other N–S-striking faults’ roles of the Regensburg–Leipzig–Rostock zone for upper mantle degassing might have been underestimated previously. © 2015, Springer-Verlag Berlin Heidelberg. Article 2015 English 14373254 10.1007/s00531-014-1140-4 International Journal of Earth Sciences 104 Springer Verlag 2107 – 2129 8 Cheb Basin; Czech Republic; Karlovarsky; carbon dioxide; carbon emission; carbon flux; degassing; electrical method; electrical resistivity; gravity survey https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945459789&doi=10.1007%2fs00531-014-1140-4&partnerID=40&md5=8fe19a5ebecd6c18d611e6aab81e8352 Cited by: 34 Tobias Nickschick Horst Kämpf Christina Flechsig Jan Mrlina Jens Heinicke article Fischer20141 Earthquake swarms and high CO2 flow of mantle origin are the characteristic features of West Bohemia/Vogtland (Central Europe). At present, the highest concentration of earthquake activity and CO2 degassing occurs in the area of the Cheb Basin at the intersection of the Eger Rift and Regensburg-Leipzig-Rostock Zone with three Quaternary active volcanoes. We review about 140 studies on structure, tectonics, volcanism, seismicity, earthquake source, triggering mechanisms, and gas-isotope geochemistry focused on the earthquake swarms from this area with the aim to build a complex image of the ongoing processes and find a possible link between activity of the mantle-derived fluids and the earthquake swarms. The so far unpublished data on the 2011 swarm and little known data on the 1824 swarm are presented, as well, showing that earthquake swarms activate a complex fault system and display long-term migration that differs from the occurrence of CO2 escapes. The activity of individual swarms is consistent with models involving high-pressure fluids; the isotopic signature of the rising gas proves its origin at depths below the hypocenters. We show that the earthquake swarms and degassing of CO2 of magmatic origin represent common result of the geodynamic activity of the area. Nevertheless, current knowledge does not preclude processes other than fluid-induced failure in triggering swarm seismicity. © 2013 Elsevier B.V. Review 2014 English 00401951 10.1016/j.tecto.2013.11.001 Tectonophysics 611 1 – 27 Bohemia; Cheb Basin; Czech Republic; Germany; Karlovarsky; Vogtland; Carbon dioxide; Degassing; Exploratory geochemistry; Fluids; Geodynamics; Isotopes; Complex fault system; Earthquake swarms; Earthquake triggering; High-pressure fluids; Isotopic signatures; Triggering mechanism; Vogtland; West Bohemia; carbon dioxide; degassing; earthquake hypocenter; earthquake swarm; earthquake trigger; geochemistry; geodynamics; seismic source; seismicity; seismotectonics; trigger mechanism; volcanism; Earthquakes https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891556616&doi=10.1016%2fj.tecto.2013.11.001&partnerID=40&md5=e03105e5ecd2e1dfe20493a49dc73fdd Cited by: 146 T. Fischer J. Horálek P. Hrubcová V. Vavryčuk K. Bräuer H. Kämpf article Bräuer20145613 The Vogtland and NW Bohemia region is known for its earthquake swarms; the most intensive swarm since 1985/86 occurred in October 2008. To find further indications for the interaction of ascending mantle-derived fluids and the occurrence of earthquake swarms, detailed fortnightly studies of gas compositions (CO2, N2, Ar, He, H2, and CH 4) and isotope ratios (δ13C, δ15N, and 3He/4He) were carried out between October 2008 and April 2011 at four locations close to the Nový Kostel focal zone and at the Wettinquelle spring (Bad Brambach). From the start of the 2008 earthquake swarm seismically induced isotope-geochemical anomalies were recorded at locations along the Počatky-Plesná fault zone (PPZ) and were, for the first time, also found at degassing locations on the Mariánské LáznÄ• fault zone (MLF). Variations were observed in both the temporal and spatial distributions of the anomalies as well in anomaly strengths, probably due to the positions of these fault zones relative to the focal zone, and to differences in fluid migration pathways. Prior to both the 2000 and 2008 swarms, 3He/4He ratios>6Ra were recorded at the Bublák mofette. These anomalous pre-seismic 3He/ 4He ratios suggest that both the 2000 and 2008 swarms may have been associated with the supply of fresh magma from a less degassed reservoir in the lithospheric mantle. The temporal δ13CCO2 pattern from detailed studies at Bublák between 2005 and 2011 indicates progressive magma degassing, as well as seismically induced variations in the δ13C, providing additional support to the interpretation derived from the 3He/4He ratios. Key Points Isotope anomalies detected in gases from different faults after earthquakes A pre-seismic increase in 3He/4He (> 6 Ra) indicates magma ascent from mantle Isotope monitoring is an excellent way to track active geodynamic processes ©2014. American Geophysical Union. All Rights Reserved. Article 2014 English 21699313 10.1002/2014JB011044 Journal of Geophysical Research: Solid Earth 119 Blackwell Publishing Ltd 5613 – 5632 7 Bohemia; Czech Republic; Germany; Vogtland; carbon dioxide; carbon isotope; degassing; earthquake swarm; earthquake trigger; fault zone; geodynamics; helium isotope; igneous geochemistry; intraplate process; isotopic analysis; isotopic ratio; magmatism; nitrogen isotope; spatial distribution; temporal distribution https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906074681&doi=10.1002%2f2014JB011044&partnerID=40&md5=c17119711e016780b2512a316e76a5a6 Cited by: 27; All Open Access, Green Open Access Karin Bräuer Horst Kämpf Gerhard Strauch article Sandig20141421 Our study at this natural analog site contributes to the evaluation of methods within a hierarchical monitoring concept suited for the control of CO2 degassing. It supports the development of an effective monitoring concept for geological CO2 storage sites-carbon capture and storage as one of the pillars of the European climate change efforts. This study presents results of comprehensive investigations along a 500-m long profile within the Hartoušov (Czech Republic) natural CO2 degassing site and gives structural information about the subsurface and interaction processes in relation to parameters measured. Measurements of CO2 concentrations and investigation of the subsurface using electrical resistivity tomography and self-potential methods provide information about subsurface properties. For their successful application it is necessary to take seasonal variations (e.g., soil moisture, temperature, meteorological conditions) into consideration due to their influence on these parameters. Locations of high CO2 concentration in shallow depths are related to positive self-potential anomalies, low soil moistures and high resistivity distributions, as well as high δ13C values and increased radon concentrations. CO2 ascends from deep geological sources via preferential pathways and accumulates in coarser sediments. Repetition of measurements (which includes the effects of seasonal variations) revealed similar trends and allows us to identify a clear, prominent zone of anomalous values. Coarser unconsolidated sedimentary layers are beneficial for the accumulation of CO2 gas. The distribution of such shallow geological structures needs to be considered as a significant environmental risk potential whenever sudden degassing of large gas volumes occurs. © 2014 Springer-Verlag Berlin Heidelberg. Article 2014 English 18666280 10.1007/s12665-014-3242-5 Environmental Earth Sciences 72 Springer Verlag 1421 – 1434 5 Czech Republic; Carbon; Carbon capture; Climate change; Degassing; Electric conductivity; Geology; Moisture; Risk assessment; Soil moisture; Soils; Electrical resistivity tomography; Evaluation of methods; Meteorological condition; Permeable structures; Preferential pathways; Self potential; Self-potential anomalies; Structural information; carbon dioxide; carbon sequestration; climate change; comparative study; degassing; electrical resistivity; leakage; permeability; radon; risk assessment; underground storage; Carbon dioxide https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901574265&doi=10.1007%2fs12665-014-3242-5&partnerID=40&md5=9d467d658530b16dc8297e3ff0562231 Cited by: 12 Claudia Sandig Uta Sauer Karin Bräuer Ulrich Serfling Claudia Schütze article Horálek2013979 An earthquake swarm of magnitudes up to ML = 3.2 occurred in the region of West Bohemia/Vogtland (border area between Czech Republic and Germany) in autumn 2000. This swarmconsisted of nine episodic phases and lasted 4 months. We retrieved source mechanisms of 102 earthquakes with magnitudes between ML = 1.6 and 3.2 applying inversion of the peak amplitudes of direct P and SH waves, which were determined from ground motion seismograms. The investigated events cover the whole swarm activity in both time and space. We use data from permanent stations of seismic network WEBNET and from temporal stations, which were deployed in the epicentral area during the swarm; the number of stations varied from 7 to 18. The unconstrained moment tensor (MT) expression of the mechanism, which describes a general system of dipoles, that is both double-couple (DC) and non-DC sources, was applied. MTs of each earthquake were estimated by inversion of three different sets of data: P-wave amplitudes only, P- and SH-wave amplitudes and P-wave amplitudes along with the SH-wave amplitudes from a priori selected four 'base' WEBNET stations, the respective MT solutions are nearly identical for each event investigated. The resultant mechanisms of all events are dominantly DCs with only insignificant non-DC components mostly not exceeding 10 per cent. We checked reliability of the MTs in jackknife trials eliminating some data; we simulated the mislocation of hypocentre or contaminated the P- and SH-wave amplitudes by accidental errors. These tests proved stable and well constrained MT solutions. The massive dominance of the DC in all investigated events implies that the 2000 swarmconsisted of a large number of pure shears along a fault plane. The focal mechanisms indicate both oblique-normal and oblique-thrust faulting, however, the oblique-normal faulting prevails. The predominant strikes and dips of the oblique-normal events fit well the geometry of the main fault plane Nov'y Kostel (NK) and also match the strike, dip and rake of the largest ML =4.6 earthquake of a strong swarm in 1985/86. On the contrary, the 2000 source mechanisms differ substantially from those of the 1997-swarm (which took place in two fault segments at the edge of the main NK fault plane) in both the faulting and the content of non-DC components. Further, we found that the scalar seismic moment M0 is related to the local magnitude ML used by WEBNET as M0 ∝ 101.12ML, which differs from the scaling law using moment magnitude Mw, that is M0 ∝ 101.5 ML. © The Authors 2013. Article 2013 English 1365246X 10.1093/gji/ggt138 Geophysical Journal International 194 979 – 999 2 Bohemia; Czech Republic; Germany; Vogtland; Faulting; Seismic waves; Shear waves; Accidental error; Dynamics and mechanics of faulting; Earthquake source observations; Earthquake swarms; Fracture and flows; Intra-plate process; Moment magnitudes; Source mechanisms; data inversion; earthquake magnitude; earthquake swarm; faulting; focal mechanism; ground motion; intraplate process; moment tensor; P-wave; SH-wave; source parameters; Earthquakes https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880280912&doi=10.1093%2fgji%2fggt138&partnerID=40&md5=0056e66f9256a130fe6dba40fcef1cab Cited by: 18; All Open Access, Bronze Open Access Josef Horálek Jan Šílený article Dahm2013957 Crustal earthquake swarms are an expression of intensive cracking and rock damaging over periods of days, weeks or month in a small source region in the crust. They are caused by longer lasting stress changes in the source region. Often, the localized stressing of the crust is associated with fluid or gas migration, possibly in combination with pre-existing zones of weaknesses. However, verifying and quantifying localized fluid movement at depth remains difficult since the area affected is small and geophysical prospecting methods often cannot reach the required resolution. We apply a simple and robust method to estimate the velocity ratio between compressional (P) and shear (S) waves (vP/vS-ratio) in the source region of an earthquake swarm. The vP/vP-ratio may be unusual small if the swarm is related to gas in a porous or fractured rock. The method uses arrival time difference between P and S waves observed at surface seismic stations, and the associated double differences between pairs of earthquakes. An advantage is that earthquake locations are not required and the method seems lesser dependent on unknown velocity variations in the crust outside the source region. It is, thus, suited for monitoring purposes. Applications comprise three natural, mid-crustal (8-10 km) earthquake swarms between 1997 and 2008 from the NW-Bohemia swarm region. We resolve a strong temporal decrease of vP/vP before and during the main activity of the swarm, and a recovery of vP/vP to background levels at the end of the swarms. The anomalies are interpreted in terms of the Biot-Gassman equations, assuming the presence of oversaturated fluids degassing during the beginning phase of the swarm activity. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society. Article 2013 English 1365246X 10.1093/gji/ggt410 Geophysical Journal International 196 957 – 970 2 Bohemia; Czech Republic; Geophysical prospecting; Shear flow; Tomography; Transport properties; Velocity; Crustal earthquakes; Double differences; Earthquake location; Earthquake source observations; Earthquake swarms; Monitoring purpose; Velocity variations; Volcano seismology; anomaly; arrival time; earthquake swarm; P-wave; S-wave; seismic source; seismic tomography; seismic velocity; seismology; Earthquakes https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891559309&doi=10.1093%2fgji%2fggt410&partnerID=40&md5=eb58ca41b921ba4b961994e5b5174b12 Cited by: 23; All Open Access, Green Open Access, Hybrid Gold Open Access Torsten Dahm Tomáš Fischer article Růzek20131251 In this paper, we present a smooth 3-D seismic model WB2012 for theWest Bohemia/Vogtland earthquake swarm region derived by means of seismic tomography. Inverted data were represented by a set of 2920 P-wave traveltimes from controlled shots fired in a framework of different experiments and a set of 11339 P- and S-wave arrival times from 661 local earthquakes between 1991 December and 2010 March. We used a standard tomographic approach for independent calculation of P- and S-wave velocity fields in a rectangular grid whose size was 1 km in all coordinates. The traveltimes and rays were calculated by a numerical solution of the eiconal equation. While locating seismic events, our new WB2012 model yielded arrival time residuals on average by 13 per cent lower and hypocentre depths by 0.95 km shallower compared to the locations of the foci in the standard 1-D vertically inhomogeneous isotropic velocity model of the West Bohemia swarm region WB2005. Further, we converted the Pand S-wave velocities to the bulk modulus K and Poisson's ratio ν. The bulk modulus (~40- 70 GPa) correlates acceptably with the tectonic and geological structure of the area. The anomalously low values of the Poisson's ratio (~0.15) are typical for the most active focal zones of Nový Kostel and Lazy in West Bohemia. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society. Article 2013 English 1365246X 10.1093/gji/ggt295 Geophysical Journal International 195 1251 – 1266 2 Bohemia; Czech Republic; Germany; Vogtland; Earthquakes; Elastic moduli; Poisson ratio; Seismic waves; Seismographs; Shear waves; Velocity; Wave propagation; Body waves; Controlled-source seismologies; Crustal structure; Europe; Seismic tomography; arrival time; body wave; bulk modulus; crustal structure; earthquake hypocenter; earthquake swarm; isotropy; P-wave; Poisson ratio; S-wave; seismic data; seismic source; seismic tomography; seismic velocity; seismic zone; seismology; tectonic setting; three-dimensional modeling; Three dimensional https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885811978&doi=10.1093%2fgji%2fggt295&partnerID=40&md5=2d75e5c95ca7f10a63de9a2fb38ac9be Cited by: 17; All Open Access, Bronze Open Access Bohuslav Růžek Josef Horálek article Hrubcová2013120 The West Bohemia/Vogtland area is known for its increased geodynamic activity with reoccurrence of intraplate earthquake swarms. Previous geophysical studies, namely active and passive seismic investigations, revealed a high velocity lower crust in this area with increased reflectivity. To refine this result and retrieve a more detailed structure of the deep crust and the Moho discontinuity, we analyzed waveforms of local microearthquakes that occurred in this area during the 2008 swarm. The waveforms of earthquakes were grouped into clusters with similar focal mechanisms, and the clusters were processed separately. We developed a new multiazimuthal approach in data processing to increase resolution of Moho phases in the waveforms. We applied the waveform cross-correlation of the P and S waves, and rotated, aligned, and stacked the seismograms to extract the Moho SmS, PmP, and PmS reflected/converted phases. These phases were inverted for laterally varying Moho depth by ray tracing and a grid search inversion algorithm. The model retrieved was verified using modeling of full waveforms computed by the discrete wave number method. The multiazimuthal approach reveals details in the velocity structure of the crust/mantle transition at each station. Instead of a single interface with a sharp velocity contrast, the inversion indicates a reflective zone at Moho depths with one or two strongly reflective interfaces, which is in agreement with the zone interpreted by previous investigations. The thickness of the zone varies from 2 to 4 km within the depth range of 27-31.5 km and is delimited by reflections from its top and bottom boundaries, sometimes with strong reflectors within the zone. The average Vp/Vs ratio determined from the Moho reflections and conversions is 1.73. Key Points Moho topography from waveforms of local microearthquakes New multi-azimuthal approach to reveal details of the crust/mantle transition Combined data processing, ray tracing, discrete wave-number and grid search ©2012. American Geophysical Union. All Rights Reserved. Article 2013 English 21699313 10.1029/2012JB009360 Journal of Geophysical Research: Solid Earth 118 Blackwell Publishing Ltd 120 – 137 1 Bohemia; Bohemian Massif; Czech Republic; Germany; Vogtland; crustal structure; focal mechanism; lower crust; microearthquake; modeling; Moho; P-wave; S-wave; seismicity; velocity structure; waveform analysis https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877110777&doi=10.1029%2f2012JB009360&partnerID=40&md5=498aa8c3e7cc8b556cdf04baa02b0b66 Cited by: 27 Pavla Hrubcová Václav Vavryčuk Alena Boušková Josef Horálek article Vavryčuk2013189 We have analyzed 463 micro-earthquakes in the magnitude range from 0.5 to 3.8 that occurred during the 2008 earthquake swarm in West Bohemia, Czech Republic, in order to screen the detailed structure of the focal zone situated at depths between 7 and 11. km. The double-difference location method was applied to records of 22 local seismic stations with an epicentral distance of less than 25. km in order to retrieve highly accurate locations of hypocenters with an accuracy of less than 20. m. The hypocenters are well-clustered and distinctly map the system of activated faults. The fault system has a complex geometry being composed of several fault segments with different orientations. Some of the segments intersect each other. The orientations of the segments coincide well with the focal mechanisms. We have introduced and evaluated the so-called fault instability of the individual fault segments. The fault instability ranges from 0 (most stable faults) to 1 (most unstable faults) and measures the susceptibility of the fault to be activated under specified stress. In the West Bohemia focal zone, two fault segments are optimally oriented with respect to the tectonic stress being characterized by an instability value higher than 0.9. Tractions on these fault segments are concentrated in the Mohr's diagram in the area of validity of the Mohr-Coulomb failure criterion and the associated micro-earthquakes are mainly shear. The other fault segments are slightly misoriented with instability values between 0.7 and 0.9, and the shear traction is significantly lower. These earthquakes are probably more tensile and activated most likely by the local redistribution of Coulomb stress during swarm activity. © 2013 Elsevier B.V. Article 2013 English 00401951 10.1016/j.tecto.2013.01.025 Tectonophysics 590 189 – 195 Bohemia; Czech Republic; Earthquakes; Stability; Earthquake location; Failure criteria; Fault friction; Focal mechanism; Tectonic stress; Coulomb criterion; earthquake event; earthquake hypocenter; earthquake magnitude; focal mechanism; image resolution; microearthquake; Faulting https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875375854&doi=10.1016%2fj.tecto.2013.01.025&partnerID=40&md5=113001a50720526c03138c06ce101ce2 Cited by: 71 Václav Vavryčuk Fateh Bouchaala Tomáš Fischer article Dahm201393 2013 English 18168957 10.5194/sd-16-93-2013 Scientific Drilling 93-99 GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany; Institute of Geophysics, Academy of Science, 141 31 Prague, Czech Republic; Faculty of Science, Charles University in Prague, Albertov 6, 128 43, Prague, Czech Republic; Institute of Geophysics and Geoinformatics, TU Bergakademie Freiberg, 09599 Freiberg, Germany; Institut für Geophysik und Geologie, Universität Leipzig, Talstraße 35, 04103 Leipzig, Germany; Institute of Earth and Environmental Sciences, University of Potsdam, Karl-Liebknecht-Str. 24, 14476 Golm, Germany 16 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892843755&doi=10.5194%2fsd-16-93-2013&partnerID=40&md5=2f27bf68246038e0ed55bbd32fbdcaef cited By 17 T. Dahm P. Hrubcová T. Fischer J. Horálek M. Korn D. Wagner article Kämpf201371 In the western Eger Rift (ER) area along the Počatky-Plesná fault zone (PPZ) CO2 degassing occurs predominantly within two mofette fields Bublák and Hartoušov. We studied 27 wet mofettes belonging to these mofette fields for gas emission rates repeatedly between 2007 and 2009 and selected mofettes for gas composition and isotope ratios (δ13C, 3He/4He). Detailed ground mapping along the PPZ provided further two separated diffuse degassing structures (DDS) within the mofette fields Hartoušov and Bublák. The DDS Hartoušov was studied in detail by measurements of 682 CO2 soil gas concentrations, 762 CO2 soil gas fluxes (max. 10 grid spacing) and partly by analyses of isotope ratios (13C/12C, 3He/4He) of soil gas. At the DDS Hartoušov the total CO2 soil flux yielded 1.559tm-2d-1 in spring 2009 and the CO2 emission rate at the wet mofettes of Hartoušov mofette field yielded 0.62td-1. The total CO2 discharge of the 27 wet mofettes was 3.75t d-1.At sites with high CO2 soil flux, the portion of mantle-derived helium is in the same range as the releasing at wet mofettes; both cover the signature of the subcontinental mantle. Also, the δ13C values analysed in the gas releasing from wet mofettes and those analysed in soil gas are nearly the same. Taking in account a biogenic soil CO2 flux of 25gm-2d-1 as background, the mantle-derived CO2 flux yielded approximately 1566tm-2d-1. As a result of the CO2 flux mapping of the DDS Hartoušov, it could be proved that 97.4% of the released soil CO2 (1.518tm-2d-1) stems from sites with CO2 fluxes higher than 500gm-2d-1-pointing to dominantly fault-related CO2 release.At the central mofette Bublák (B2), the gas emission rate was determined for the first time in 1993. Measurements repeated between 2007 and 2009 showed a clear increase in the gas emission rate of more than 40%, correlating well with the increase of the 3He/4He ratios from 5Ra to approximately 6Ra between 1993 and 2008 at this location (Bräuer et al., 2009).The Bublák mofette field is characterised by the highest CO2 emission rate along the PPZ, and in combination with the helium isotope signature of the European subcontinental mantle, this area was identified as a deep-reaching fluid injection zone. © 2012 Elsevier B.V. Article 2013 English 00092541 10.1016/j.chemgeo.2012.08.005 Chemical Geology 339 71 – 83 Czech Republic; Degassing; Gas emissions; Geologic models; Helium; Isotopes; Particulate emissions; Radium; Soils; C values; Continental rift; Czech Republic; Diffuse degassing; Eger Rift; Emission rates; Fault zone; Fluid injections; Gas compositions; Gas emission rates; Gas releasing; Grid-spacings; Ground mapping; Helium isotopes; Isotope ratio; ; Measurements of; Soil CO; Soil flux; Soil gas; Soil gas concentration; Subcontinental mantle; Total CO; carbon dioxide; carbon emission; carbon flux; degassing; diffusion; fluid injection; helium isotope; isotopic analysis; isotopic composition; isotopic ratio; rifting; soil gas; Carbon dioxide https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873748876&doi=10.1016%2fj.chemgeo.2012.08.005&partnerID=40&md5=204b2364c33bb4beb520b1cfa0dbb787 Cited by: 71 Horst Kämpf Karin Bräuer Jens Schumann Kai Hahne Gerhard Strauch article Novotný2013491 The West Bohemia and adjacent Vogtland are well known for quasi-periodical earthquake swarms persisting for centuries. The seismogenic area near Nový Kostel involved about 90 % of overall earthquake activity clustered here in space and time. The latest major earthquake swarm took place in August-September 2011. In 1994 and 1997, two minor earthquake swarms appeared in another location, near Lazy. Recently, the depth-recursive tomography yielded a velocity image with an improved resolution along the CEL09 refraction profile passing between these swarm areas. The resolution, achieved in the velocity image and its agreement with the inverse gravity modeling along the collateral 9HR reflection profile, enabled us to reveal the key structural background of these West Bohemia earthquake swarms. The CEL09 velocity image detected two deeply rooted high-velocity bodies adjacent to the Nový Kostel and Lazy focal zones. They correspond to two Variscan mafic intrusions influenced by the SE inclined slab of Saxothuringian crust that subducted beneath the Teplá-Barrandian terrane in the Devonian era. In their uppermost SE inclined parts, they roof both focal zones. The high P-wave velocities of 6,100-6,200 m/s, detected in both roofing caps, indicate their relative compactness and impermeability. The focal domains themselves are located in the almost gradient-free zones with the swarm foci spread near the axial planes of profound velocity depressions. The lower velocities of 5,950-6,050 m/s, observed in the upper parts of focal zones, are indicative of less compact rock complexes corrugated and tectonically disturbed by the SE bordering magma ascents. The high-velocity/high-density caps obviously seal the swarm focal domains because almost no magmatic fluids of mantle origin occur in the Nový Kostel and Lazy seismogenic areas of the West Bohemia/Vogtland territory, otherwise rich in the mantle-derived fluids. This supports the hypothesis of the fluid triggering of earthquake swarms. The sealed focal domains retain ascending magmatic fluids until their critical pressure and volumes accumulated cause rock micro-fractures perceived as single earthquake bursts. During a swarm period, the focal depths of these sequential events become shallower while their magnitudes grow. We assume that coalescence of the induced micro-fractures forms temporary permeability zones in the final swarm phase and the accumulated fluids release into the overburden via the adjacent fault systems. The fluid release usually occurs after the shallowest events with the strongest magnitudes ML &gt; 3. The seasonal summer declines of hydrostatic pressure in the Cheb Basin aquifer system seem to facilitate and trigger the fluid escape as happened for the 2000, 2008, and 2011 earthquake swarms. The temporary fluid release, known as the valve-fault action, influences the surface aquifer systems in various manners. In particular, we found three quantities, the strain, mantle-derived 3He content in CO2 surface sources and ground water levels, which display a 3-5 months decline before and then a similar restoration after each peak earthquake during the swarm activities. The revealed structure features are particularly important since the main Nový Kostel earthquake swarm area is proposed as a site for the ICDP project, 'Eger Rift Drilling'. © 2013 Springer Science+Business Media Dordrecht. 2013 English 01693298 10.1007/s10712-013-9239-x Surveys in Geophysics 34 Kluwer Academic Publishers 491-519 Institute of Geophysics ASCR, Prague, Czech Republic; Institute of Petroleum Engineering, TU Clausthal, Agricolastrasse 10, Clausthal-Zellerfeld, Germany 4 Aquifers; Faulting; Groundwater resources; Hydrostatic pressure; Image enhancement; Inverse problems; Refraction; Roofs; Seismic waves; Structure (composition); Tomography; Velocity; Water levels, 9hr reflection profiles; Bohemian massifs; CEL09 refraction profiles; Earthquake swarms; Gravity model; Saxothuringian, Earthquakes, earthquake magnitude; earthquake mechanism; earthquake swarm; gravity field; Hercynian orogeny; hydrostatic pressure; inverse analysis; refraction; slab; subduction; tomography, Bohemian Massif; Cheb Basin; Czech Republic; Germany; Karlovarsky; Vogtland https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879844941&doi=10.1007%2fs10712-013-9239-x&partnerID=40&md5=b7a11f44e7385a6ea0fefcee647cad13 cited By 3 M. Novotný A. Špičák F.H. Weinlich article Fischer20121019 Geodynamic activity in the area of West Bohemia is typified by the occurrence of earthquake swarms, Quaternary volcanism and high flux of mantle-derived CO2. The highest swarm activity occurs beneath the eastern edge of the Cheb basin, which is delineated by the NW-SE trending morphologically pronounced Mariánské Lázně Fault (MLF) controlling the formation of the basin. The previous trenching survey across the MLF zone has identified several fault strands with possible Quaternary activity. In this paper we present the results of the geophysical survey focused to trace the faults signatures in geophysical sections and to build an image of near surface tectonics. The method of electric resistivity tomography (ERT) along two profiles parallel to the trench identified a strong resistivity contrast between the bodies of sandy gravels in the middle and conductive clayey sands to the west and weathered crystalline basement to the east. The 2-D ground penetration radar (GPR) sections show direct correlation of reflections with lithological boundaries identified in the trench. As expected, the GPR signal amplitudes increase with the resistivities found in the ERT sections. Two of the four faults identified in the trench are indicated in the resistivity and GPR sections. A 3-D GPR measurement has identified a spot of high amplitudes elongated parallel to the MLF trend, which coincides with the high resistivity body. To improve the signal-to-noise ratio of the time slices we stacked the GPR time slices within vertically homogeneous blocks. This provided a contrast image of the sand-gravel body including its boundaries in three dimensions. The detailed analysis of the 3-D GPR cube revealed additional fault that limits the highly reflective sands and appears to be offset by another younger fault. Our results suggest a complex fault pattern in the studied area, which deserves a further study. © 2012 Institute of Geophysics of the ASCR, v.v.i. Article 2012 English 00393169 10.1007/s11200-012-0825-z Studia Geophysica et Geodaetica 56 Kluwer Academic Publishers 1019 – 1036 4 Bohemia; Czech Republic; earthquake swarm; electrical resistivity; fault zone; geodynamics; ground penetrating radar; lithology; Quaternary; signal-to-noise ratio; three-dimensional modeling; tomography; trend analysis; two-dimensional modeling; volcanism https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870856355&doi=10.1007%2fs11200-012-0825-z&partnerID=40&md5=ed2fff6455ae6d6221069cbd495f0ba1 Cited by: 16 Tomáš Fischer Petra Štěpančíková Magda Karousová Petr Tábořík Christina Flechsig Mahmoud Gaballah article Geissler201212 In 2004 and 2005 a passive seismic experiment was carried out in the northern and northeastern part of the Bohemian Massif (Sudetes) to study the lithospheric structure. We present results from Ps and Sp receiver function analyses. With one exception, Moho depth at stations in the northwestern part of the study area varies between 28 and 32km. Thicker crust up to 35km was mapped toward the south (Moldanubian unit) and toward the east (Moravo-Silesian and Brunovistulian units) confirming results from previous active seismic measurements. There exists a relatively sharp step in Moho depth between units of the central Sudetes (~30km) and the Moravo-Silesian unit (~35km). The v p/v s ratios inverted from primary and multiple Moho Ps conversions hint for different crustal compositions of the units. Toward the Carpathian thrust we have no clear indications for any crustal root or slab beneath the western Carpathians. However, our data suggests a deepening of the Moho or at least a complicated crust-mantle transition in this area. Additional Ps phases were observed between 6 and 10s delay time in the Sudetes. These phases cannot be explained by Moho reverberations, but are most probably caused by low velocity zones in the middle crust or lithospheric mantle as shown by modeling of theoretical receiver functions. The stations showing these abnormal phases are located in the area of Permo-Carboniferous basins on probably Teplá-Barrandian crust. Therefore we assume that the phases hint at a mid-crustal low velocity zone between 16 and 20km depth, which is interpreted as a felsic solidified magma reservoir of the Permo-Carboniferous volcanism beneath the Sudetic Basins. Sp receiver functions show phases with negative polarity at 9 to 12s lead time on average, which we interpret as lithosphere-asthenosphere boundary at about 80 to 110km depth. © 2012 Elsevier B.V. Review 2012 English 00401951 10.1016/j.tecto.2012.05.005 Tectonophysics 564-565 12 – 37 Bohemian Massif; Sudetes; Seismology; Central Europe; ratio; Lithosphere-asthenosphere boundary; Lithospheric structure; Moho discontinuity; Permo-Carboniferous volcanism; asthenosphere; Carboniferous; crust-mantle boundary; crustal structure; lithospheric structure; magma chamber; Moho; observational method; Permian; S-wave; seismic tomography; seismic velocity; velocity structure; volcanism; Structural geology https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865163267&doi=10.1016%2fj.tecto.2012.05.005&partnerID=40&md5=fdf1dfe64b5aaaa898d13c96d2b55d67 Cited by: 23 Wolfram H. Geissler Horst Kämpf Zuzana Skácelová Jaroslava Plomerova Vladislav Babuška Rainer Kind article Hiemer2012169 The most recent intense earthquake swarm in West Bohemia lasted from 6 October 2008 to January 2009. Starting 12 days after the onset, the University of Potsdam monitored the swarm by a temporary small-aperture seismic array at 10 km epicentral distance. The purpose of the installation was a complete monitoring of the swarm including micro-earthquakes (M L < 0). We identify earthquakes using a conventional short-term average/long-term average trigger combined with sliding-window frequency-wavenumber and polarisation analyses. The resulting earthquake catalogue consists of 14,530 earthquakes between 19 October 2008 and 18 March 2009 with magnitudes in the range of - 1.2 ≤ M L ≤ 2. 7. The small-aperture seismic array substantially lowers the detection threshold to about M c = - 0.4, when compared to the regional networks operating in West Bohemia (M c > 0.0). In the course of this work, the main temporal features (frequency-magnitude distribution, propagation of back azimuth and horizontal slowness, occurrence rate of aftershock sequences and interevent-time distribution) of the recent 2008/2009 earthquake swarm are presented and discussed. Temporal changes of the coefficient of variation (based on interevent times) suggest that the swarm earthquake activity of the 2008/2009 swarm terminates by 12 January 2009. During the main phase in our studied swarm period after 19 October, the b value of the Gutenberg-Richter relation decreases from 1.2 to 0.8. This trend is also reflected in the power-law behavior of the seismic moment release. The corresponding total seismic moment release of 1.02×10 17 Nm is equivalent to M L,max = 5. 4. © 2011 Springer Science+Business Media B.V. Article 2012 English 13834649 10.1007/s10950-011-9256-5 Journal of Seismology 16 169 – 182 2 Bohemia; Czech Republic; aftershock; earthquake catalogue; earthquake magnitude; earthquake swarm; frequency analysis; microearthquake; monitoring; polarization; seismic moment; temporal variation https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858156392&doi=10.1007%2fs10950-011-9256-5&partnerID=40&md5=eb1a23b70e199da3a3ad271441ebd5ba Cited by: 15 Stefan Hiemer Dirk Roessler Frank Scherbaum article Hainzl2012271 Two recent major swarms in Western Bohemia occurred in the years 2000 and 2008 within almost the same portion of a fault close to Novy Kostel. Previous analysis of the year 2000 earthquake swarm revealed that fluid intrusion seemed to initiate the activity whereas stress redistribution by the individual swarm earthquakes played a major role in the further swarm evolution. Here we analyse the new swarm, which occurred in the year 2008, with regard to its correlation to the previous swarm as well its spatiotemporal migration patterns. We find that (i) the main part of the year 2008 activity ruptured fault patches adjacent to the main activity of the swarm 2000, but that also (ii) a significant overlap exists where earthquakes occurred in patches in which stress had been already released by precursory events; (iii) the activity shows a clear migration which can be described by a 1-D (in up-dip direction) diffusion process; (iv) the migration pattern can be equally well explained by a hydrofracture growth, which additionally explains the faster migration in up-dip compared to the down-dip direction as well as the maximum up-dip extension of the activity. We use these observations to estimate the underlying fluid pressure change in two different ways: First, we calculate the stress changes induced by precursory events at the location of each swarm earthquake assuming that observed stress deficits had to be compensated by pore pressure increases; and secondly, we estimate the fluid overpressure by fitting a hydrofracture model to the asymmetric seismicity patterns. Both independent methods indicate that the fluid pressure increase was initially up to 30 MPa. © 2012 The Authors Geophysical Journal International © 2012 RAS. Article 2012 English 1365246X 10.1111/j.1365-246X.2012.05610.x Geophysical Journal International 191 271 – 281 1 Bohemia; Czech Republic; Diffusion in liquids; Estimation; Faulting; Diffusion process; Earthquake dynamics; Earthquake source; Earthquake swarms; Fluid pressures; Hydro-fracture; Migration patterns; Overpressure; Pressure increase; Seismicity pattern; Stress changes; Stress redistribution; earthquake precursor; earthquake swarm; fault; fluid pressure; fracture; geostatistics; seismic migration; seismic source; seismicity; seismology; Earthquakes https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866418087&doi=10.1111%2fj.1365-246X.2012.05610.x&partnerID=40&md5=8b6aea5945b37654c079243b8a9acc4d Cited by: 66; All Open Access, Bronze Open Access, Green Open Access S. Hainzl T. Fischer T. Dahm article Bräuer2011163 We report new data on gas and isotope compositions of mantle-derived exhalations from five locations in the Vogtland (Germany)/NW Bohemia (Czech Republic) area, close to the Nový Kostel focal zone, recorded by monthly sampling of gases over a three year period. This region is the locus typicus for the term "earthquake swarm"; since 1985/86 the largest numbers of earthquake swarms in the Vogtland/NW Bohemia have occurred in the Nový Kostel focal zone. Mantle-derived degassing has been studied at four locations within the Cheb Basin degassing centre, and at the Wettinquelle spring to the north on the edge of the Cheb Basin. The Bublák and U Mostku locations are on the Počatky Plesná Fault Zone (PPZ) while the Kopanina and Dolni Častkov locations are on the Mariánské Lázně Fault (MLF). The mantle-derived helium content at locations along the PPZ covers the range of the sub-continental lithospheric mantle (SCLM). Along the MLF the 3He/4He ratios are with up to 5.4Ra a little bit lower as at the PPZ locations. The CO2/3He ratios point to a predominantly magmatic source. Depending on the magnitude of gas flux the monthly sampling results indicated various major influences on the fluid signatures at the monitored locations due to seasonal cycles based on the different strong influence of CO2/water interaction. Micro-seismicity occurred repeatedly during the monitoring period and seismically triggered geochemical anomalies were repeatedly observed at the locations close to the focal zone. The 3He/4He ratios drop from 5.9Ra (mean) up to 5.6Ra at Bublák and from 5.6Ra up to 5.3Ra at U Mostku. A decrease in 3He/4He ratios was observed prior to seismic events due to stress accumulation before rupturing, and also after the events due to the release of crustal-derived components within the area of the focal zone. Due to the higher 'helium baseline content' of the Kopanina gas the 3He/4He ratios decreased there only from 4.6 to 4.5Ra. At the Wettinquelle, the most distant from the focal zone, the 3He/4He ratios ranged between 2.3 and 2.5Ra altogether. Superimposed to the seismically induced anomalies a clear three month-lasting increase of mantle-derived helium was observed at the locations on the PPZ. The 3He/4He ratios increased to 6.3Ra at Bublák and to 6.0Ra at U Mostku. An increase in the 3He/4He ratios was also noted at Kopanina (to 4.7Ra) and Dolni Častkov (to 5.4Ra), interpreted as indicating an ascent of less degassed magma (dyke intrusions) from the deeper lithospheric mantle reservoir. Superimposed geochemical effects initiated by the temporal and spatial evolution of a hidden magmatic-driven geodynamic process have therefore been observed in a continental rift system for the first time. © 2011 Elsevier B.V. Article 2011 English 00092541 10.1016/j.chemgeo.2011.09.012 Chemical Geology 290 163 – 176 3-4 Bohemia; Cheb Basin; Czech Republic; Germany; Karlovarsky; Vogtland; Carbon dioxide; Degassing; Earthquakes; Gases; Geochemistry; Geologic models; Helium; Isotopes; Magnetic leakage; He ratios; Cenozoic; Earthquake swarms; Magma intrusion; ; carbon dioxide; Cenozoic; degassing; earthquake swarm; focal mechanism; gas; helium isotope; igneous intrusion; isotopic composition; isotopic ratio; lithospheric structure; magma; mantle chemistry; rift zone; Focusing https://www.scopus.com/inward/record.uri?eid=2-s2.0-80055118337&doi=10.1016%2fj.chemgeo.2011.09.012&partnerID=40&md5=3a27d7c6eac830c478caddce5868437c Cited by: 52 Karin Bräuer Horst Kämpf Ulrich Koch Gerhard Strauch article Flechsig2010443 The Cheb Basin, located in the western Eger (Ohře) Rift, is part of the European Cenozoic Rift system. Although presently non-volcanic, it is the most active area within the European Rift with signs of recent geodynamic activity like emanations of mantle derived CO2, and the repeated occurrence of swarm earthquakes, which are common features in active volcanic regions. It is assumed that the fluids, uprising in permeable channels, play a key role for the genesis of these earthquake swarms. An image of the distribution of the electrical conductivity (resp. resistivity) in the upper crust can give information about the fluid distribution since the electrical patterns reflect pathways of fluids and fluid properties like ionic content. This was the motivation to start both a regional-scale direct current (DC) geoelectrical test covering the Cheb Basin area and several local-scale near surface investigations inside the basin at the seismically active faults Počátky-Plesná Zone (PPZ) and Mariánské Lázně Fault Zone (MLF) near Nový Kostel. It was the research idea to test electrical tomography's ability to detect faults and tectonic deformation in a complex geological environment and to identify characteristic features of these faults. The more methodically justified regional field test mainly aimed at clarifying the opportunity to trace DC electrical signals in an area with known high industrial noise in a sufficient quality. A field set-up with a range of 15-20 km is necessary for an investigation depth of 4-5 km in case of DC geoelectrics. A new developed inversion strategy for sparse electrical data sets allows for a first (coarse) model of resistivity distribution. The near surface investigations in prominent fault zones of the Cheb Basin give more detailed information about the structure of fault zones, divide the sedimentary units in different resistivity zones and detect vertical displacements in the quaternary formations. © 2010 Institute of Geophysics of the ASCR, v.v.i. Article 2010 English 00393169 10.1007/s11200-010-0026-6 Studia Geophysica et Geodaetica 54 443 – 463 3 Bohemia; Cheb Basin; Czech Republic; Karlovarsky; active fault; electrical conductivity; electrical resistivity; fault zone; geodynamics; geoelectric field; mantle source; numerical model; tomography; upper crust; vertical electrical sounding https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957153541&doi=10.1007%2fs11200-010-0026-6&partnerID=40&md5=325d5c3ef717472e0b96d8a0b3d27114 Cited by: 22 Christina Flechsig Tobias Fabig Carsten Rücker Claudia Schütze article Fischer2010665 A swarm of earthquakes of magnitudes up to ML = 3.8 stroke the region of West Bohemia/Vogtland (border area between Czechia and Germany) in October 2008. It occurred in the Nový Kostel focal zone, where also all recent earthquake swarms (1985/1986, 1997, and 2000) took place, and was striking by a fast sequence of macroseismically observed earthquakes. We present the basic characteristics of this swarm based on the observations of a local network WEBNET (West Bohemia seismic network), which has been operated in the epicentral area, on the Czech territory. The swarm was recorded by 13 to 23 permanent and mobile WEBNET stations surrounding the swarm epicenters. In addition, a part of the swarm was also recorded by strong-motion accelerometers, which represent the first true accelerograms of the swarm earthquakes in the region. The peak ground acceleration reached 0.65 m/s2. A comparison with previous earthquake swarms indicates that the total seismic moments released during the 1985/1986 and 2008 swarms are similar, of about 4E16 Nm, and that they represent the two largest swarms that occurred in the West Bohemia/ Vogtland region since the ML = 5.0 swarm of 1908. Characteristic features of the 2008 swarm are its short duration (4 weeks) and rapidity and, consequently, the fastest seismic moment release compared to previous swarms. Up to 25,000 events in the magnitude range of 0.5 < ML < 3.8 were detected using an automatic picker. A total of nine swarm phases can be distinguished in the swarm, five of them exceeding the magnitude level of 2.5. The magnitude-frequency distribution of the complete 2008 swarm activity shows a b value close to 1. The swarm hypocenters fall precisely on the same fault portion of the Nový Kostel focal zone that was activated by the 2000 swarm (ML ≤ 3. 2) in a depth interval from 6 to 11 km and also by the 1985/1986 swarm (ML ≤ 4.6). The steeply dipping fault planes of the 2000 and 2008 swarms seem to be identical considering the location error of about 100 m. Furthermore, focal mechanisms of the 2008 swarm are identical with those of the 2000 swarm, both matching an average strike of 170° and dip of 80° of the activated fault segment. An overall upward migration of activity is observed with first events at the bottom and last events at the top of the of the activated fault patch. Similarities in the activated fault area and in the seismic moments released during the three largest recent swarms enable to estimate the seismic potential of the focal zone. If the whole segment of the fault plane was activated simultaneously, it would represent an earthquake of ML ~5. This is in good agreement with the estimates of the maximum magnitudes of earthquakes that occurred in the West Bohemia/Vogtland region in the past. © 2010 Springer Science+Business Media B.V. Article 2010 English 13834649 10.1007/s10950-010-9189-4 Journal of Seismology 14 665 – 682 4 Bohemia; Czech Republic; Germany; Vogtland; earthquake epicenter; earthquake event; earthquake magnitude; earthquake mechanism; earthquake swarm; fault plane; focal mechanism; peak acceleration; seismic moment; seismicity; strong motion https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957229959&doi=10.1007%2fs10950-010-9189-4&partnerID=40&md5=db48c0f4fc254d1bcc35e349ca54d64d Cited by: 74; All Open Access, Green Open Access Tomáš Fischer Josef Horálek Jan Michálek Alena Boušková article Hrubcová2009275 The structure of the crust and the crust-mantle boundary in the Vogtland/ West Bohemian region have been a target of several seismic measurements for the last 25 years, beginning with the steep-angle reflection seismic studies (DEKORP-4/KTB, MVE-90, 9HR), the refraction and wide-angle experiments (GRANU'95, CELEBRATION 2000, SUDETES 2003), and followed by passive seismic studies (receiver functions, teleseismic tomography). The steep-angle reflection studies imaged a highly reflective lower crust (4 to 6 km thick) with the Moho interpreted in a depth between 30 and 32 km and a thinner crust beneath the Eger Rift. The refraction and wide-angle reflection seismic studies (CELEBRATION 2000) revealed strong wide-angle reflections in a depth of 26-28 km interpreted as the top of the lower crust. Long coda of these reflections indicates strong reflectivity in the lower crustal layer, a phenomenon frequently observed in the Caledonian and Variscan areas. The receiver function studies detected one strong conversion from the base of the crust interpreted as the Moho discontinuity at a depth between 27 and 37 km (average at about 31 km). The discrepancies in the Moho depth determination could be partly attributed to different background of the methods and their resolution, but could not fully explain them. So that new receivers function modelling was provided. It revealed that, instead of a first-order Moho discontinuity, the observations can be explained with a lower crustal layer or a crust-mantle transition zone with a maximum thickness of 5 km. The consequent synthetic ray-tracing modelling resulted in the model with the top of the lower crust at 28 km, where highly reflective lower crustal layer can obscure the Moho reflection at a depth of 32-33 km. © Institute of Geophysics of the ASCR, v.v.i 2009. Article 2009 English 00393169 10.1007/s11200-009-0018-6 Studia Geophysica et Geodaetica 53 275 – 294 3 Bohemian Massif; Central Europe; Eurasia; Europe; Germany; Vogtland; coda; crust-mantle boundary; crustal structure; lower crust; Moho; ray tracing; seismic method; seismic reflection; seismic refraction; transition zone https://www.scopus.com/inward/record.uri?eid=2-s2.0-68349127015&doi=10.1007%2fs11200-009-0018-6&partnerID=40&md5=91031464b34bb6b2ef91f70fc1b1f11b Cited by: 31 Pavla Hrubcová Wolfram H. Geissler article Faber2009315 Two stations monitoring concentrations of carbon dioxide and radon in soil gas (Oldřiášská and Nový Kostel) and one station monitoring flow of carbon dioxide at a mofette (Soos) have been operated in the area of the West Bohemian earthquake swarms. We present preliminary results obtained on the base of four-year observations. We found that data are not influenced considerably by barometric pressure. Although the CO2 concentration varies greatly, the long-term trends at stations Oldŕliíǎská and Nový Kostel are similar, which indicates that the CO2 flow is controlled by common geogenic processes. Also temporal trends of CO2 and Rn concentrations in soil gas at individual stations are analogous. We found diurnal variations of both CO2 concentration in soil gas and the CO2 flow at mofettes due to the earth tides. A response to tides of semi-diurnal period is insignificant in CO2 concentration and only weak in the CO2 flow. We also examined possible pre-seismic, co-seismic and post-seismic effects of the intensive 2008 earthquake swarm on the CO2 concentration at Oldčíšská and Nový Kostel, and on the CO2 flow at Soos. However, all potential indications were insignificant and there has not been proven any influence of the swarm on the CO2 concentration as well as on the CO2 flow. Nevertheless, a gradual decrease of amplitudes of diurnal variations before the swarm and the lowest amplitudes during the swarm is a noteworthy phenomenon, which might indicate the strain changes of the rock associated with earthquake swarm. © Institute of Geophysics of the ASCR, v.v.i 2009. Article 2009 English 00393169 10.1007/s11200-009-0020-z Studia Geophysica et Geodaetica 53 315 – 328 3 Bohemia; Central Europe; Czech Republic; Eurasia; Europe; amplitude; carbon dioxide; concentration (composition); diurnal variation; Earth tide; earthquake swarm; gas flow; radon; soil gas; time series analysis https://www.scopus.com/inward/record.uri?eid=2-s2.0-68349154321&doi=10.1007%2fs11200-009-0020-z&partnerID=40&md5=d886873e0ca150e9b81c7e32c295b043 Cited by: 20 Eckhard Faber Josef Horálek Alena Boušková Manfred Teschner Ulrich Koch Jürgen Poggenburg article Bräuer2009 The detailed processes generating earthquake swarms are complex and not fully understood. Most earthquake swarms occur in volcanic regions and mid-ocean rifts. Here, we report new 3HeZ4He data of free gases monitored at CO2rich degassing locations close to the Nový Kostel focal zone (NKFZ) located in the western Eger rift. The NKFZ is known for the recurrence of earthquake swarms at which the focal zone ranges between 6 and 12 km depth. At degassing locations neighboring to the NKFZ a progressive increase of mantle-derived helium has been observed during the last 15 years - actually the highest 3He/4He ratios (>6 Ra) in Central Europe. The 3HeZ4He anomalies indicate hidden magmatic activity. We assume that the latest strong earthquake swarm in October 2008 was initiated by a hidden magma intrusion process from the upper mantle into the lower crust that has been indicated by a three month lasting increase of the 3HeZ4He ratios in spring 2006 at all degassing locations near the NKFZ. Copyright 2009 by the American Geophysical Union. Article 2009 English 00948276 10.1029/2009GL039615 Geophysical Research Letters 36 American Geophysical Union 17 Central Europe; Eger; Eurasia; Europe; Heves; Hungary; Degassing; Helium; Oceanography; Volcanoes; Central Europe; Earthquake swarms; Focal zones; Free gas; Lower crust; Magma intrusion; Magmatic activity; Upper mantle; Volcanic region; carbon dioxide; degassing; earthquake swarm; helium; lower crust; magmatism; rift zone; upper mantle; Earthquakes https://www.scopus.com/inward/record.uri?eid=2-s2.0-71949086773&doi=10.1029%2f2009GL039615&partnerID=40&md5=4fe8816b997146aab9860df32385cda4 Cited by: 59 Karin Bräuer Horst Kämpf Gerhard Strauch article Mrlina200997 Based on results of previous investigations of tephra-tuff volcaniclastic deposits and a geophysical survey in the surroundings of the Železná hůrka Quaternary volcano, West Bohemia, we performed detailed geophysical surveys using gravimetry, magnetometry and electrical conductivity techniques. Striking anomalies were revealed in a morphological depression near Mýtina, West Bohemia, as a strong evidence of the assumed maar-diatreme structure. The sharp isometric gravity low of - 2.30 mGal, as well as the corresponding positive magnetic anomaly of 200 nT with a negative rim on its northern side indicate a steeply dipping geological body of low density and containing magnetic rocks/minerals. Magnetic survey also showed pronounced local anomalies outside the depression that can reflect relicts of the tephra rim of the maar. This geophysical evidence was then proven by an exploratory drilling near the centre of the gravity anomaly. Macroscopic on-site evaluation of the core, and more detailed sedimentological, petrochemical, palynological and microbiological laboratory analyses further confirmed the existence of a maar structure filled by 84 m of lake sediments reflecting a succession of several warm and cold climatic periods. Results of palynological analyses confirm the presence of a continuous palaeoclimate archive, with at least three successive warmer periods of most probably interstadial character from the upper Quaternary Saalian complex. Therefore, the recovered sediment sequence holds strong potential for in-depth paleoclimate reconstruction and deep biosphere studies. At the bottom of the Mýtina-1 (MY-1) borehole (84-85.5 m), country rock debris was found, containing also volcanic bombs and lapilli. The discovered volcanic structure is considered to be the first known Quaternary maar-diatreme volcano on the territory of the Bohemian Massif. Because of hidden active magmatic processes in combination with earthquake swarm seismicity ca. 20-30 km north of the Mýtina maar, reconstruction of the palaeovolcanological evolution is important for evaluation of hazard potential of the NE and E part of the Cheb Basin. © 2009 Elsevier B.V. All rights reserved. Article 2009 English 03770273 10.1016/j.jvolgeores.2009.01.027 Journal of Volcanology and Geothermal Research 182 97 – 112 1-2 Bohemian Massif; Central Europe; Eurasia; Europe; Debris; Earthquakes; Electric conductivity; Geological surveys; Geophysics; Gravitational effects; Hazards; Lakes; Minerals; Restoration; Sedimentology; Structural geology; Volcanoes; Eger Rift; geophysical survey; Quaternary maar volcanism; Saalian lake sediments; volcanic hazard potential; diatreme; earthquake swarm; electrical conductivity; geophysical survey; gravimetry; gravity anomaly; maar; magnetic anomaly; magnetometer; paleoclimate; paleoseismicity; Quaternary; Saalian; tephra; tuff; volcaniclastic deposit; Core analysis https://www.scopus.com/inward/record.uri?eid=2-s2.0-64149113281&doi=10.1016%2fj.jvolgeores.2009.01.027&partnerID=40&md5=ce0407aadd492a273d74b5657f490223 Cited by: 83 J. Mrlina H. Kämpf C. Kroner J. Mingram M. Stebich A. Brauer W.H. Geissler J. Kallmeyer H. Matthes M. Seidl article Grad2008 The SUDETES 2003 seismic experiment investigated the lithospheric structure of the eastern part of the Variscan belt of central Europe. The key profile of this experiment (S01) was 630 km long and extended southwestward from the margin of the East European craton, across the Trans-European suture zone (TESZ) and Sudetes, and across the Bohemian Massif that contains the active Eger (Ohře) rift, which is an element of the European Cenozoic rift system. Good quality first arrivals and later phases of refracted/reflected P and S waves were interpreted using 2-D ray-tracing techniques. The derived seismic model shows large variations in the internal structure of the crust, while the depth to the Moho varies in the relatively narrow depth interval of 28-35 km. Except for the Polish basin on the northeast end of the profile, the sedimentary cover is thin. The crystalline upper and middle crust with velocities of 5.9-6.4 km S-1 is about 20 km thick, and the 7-10 km thick lower crust can be divided into three regions based on P wave velocities: a low-velocity region (6.5-6.6 km s-1 beneath Eger rift and Sudetes) that is bounded on the southwest and northeast by regions of significantly higher velocity (6.8-7.1 km s-1 beneath the Saxothuringian and Moldanubian in the southwest and Fore-Sudetic Monocline and Polish Basin in the northeast). High-velocity bodies (Vp > 6.5 km s-1) were delineated in the upper crust of the Eger rift region. The seismic structure along the S01 profile images a Variscan orogenic wedge resting on the down warped margin of the plate margin containing the TESZ. This situation implies the northerly directed subduction of the Rheic Ocean that existed between the southern margin of the Old Red Continent and the Armorican terranes presently accreted into the Variscan belt. Closure of this ocean produced the Rheic suture between low-velocity crust of the Variscan orogenic wedge and higher-velocity crust of the TESZ. Copyright 2008 by the American Geophysical Union. Article 2008 English 21699313 10.1029/2007JB005497 Journal of Geophysical Research: Solid Earth 113 Blackwell Publishing Ltd 10 Bohemian Massif; Central Europe; Eurasia; Europe; Cenozoic; craton; Hercynian orogeny; lithospheric structure; low velocity zone; Moho; orogenic belt; P-wave; ray tracing; S-wave; suture zone https://www.scopus.com/inward/record.uri?eid=2-s2.0-57649243094&doi=10.1029%2f2007JB005497&partnerID=40&md5=6aa4b6d4173ae855ded2143b9bc7959c Cited by: 78 Marek Grad Aleksander Guterch Stanisław Mazur G. Randy Keller Aleš Špičák Pavla Hrubcová Wolfram H. Geissler article Dahm2008529 Earthquake swarms are often assumed to be caused by magmatic or fluid intrusions, where the stress changes in the vicinity of the intrusion control the position, strength and rate of seismicity. Fracture mechanical models of natural intrusions or man-made hydrofractures pose constraints on orientation, magnitude, shape and growing rate of fractures and can be used to estimate stress changes in the vicinity of the intrusions. Although the idea of intrusion-induced seismicity is widely accepted, specific comparisons of seismicity patterns with fracture models of stress changes are rarely done. The goal of the study is to review patterns of intrusion-induced earthquake swarms in comparison to the observations of the swarm in NW Bohemia in 2000. We analyse and discuss the theoretical 3D shape of intrusions under mixed mode loading and apparent buoyancy. The aspect ratio and form of the intrusion is used to constrain parameters of the fluid, the surrounding rock and stress. We conclude that the 2000 NW Bohemia swarm could have been driven by a magmatic intrusion. The intrusion was, however, inclined to the maximal principal stress and caused shear displacement additional to opening. We estimate that the density diference between magma and rock was small. The feeding reservoir was possibly much larger than the area affected from earthquakes and may be a vertical dike beneath the swarm region. © Institute of Geophysics of the ASCR, v.v.i 2008. Article 2008 English 00393169 10.1007/s11200-008-0036-9 Studia Geophysica et Geodaetica 52 529 – 548 4 Bohemia; Central Europe; Czech Republic; Eurasia; Europe; earthquake swarm; fracture; igneous intrusion; magmatism; modeling; seismicity; stress https://www.scopus.com/inward/record.uri?eid=2-s2.0-57549101860&doi=10.1007%2fs11200-008-0036-9&partnerID=40&md5=ee59dd20ca9e59f58c7f71b12936e638 Cited by: 27 Torsten Dahm Tom Fischer S. Hainzl article Bräuer2008 Comprehensive studies of CO2-rich fluids close to the swarm earthquake region Nový Kostel at the Czech-German border have been started 15 years ago and have in particular included two extended chemical and isotope monitoring studies lasting for several years each. The regional surface distribution patterns of the fluid signatures including the identification of the origin of fluid components are the focus of the detailed studies. Three degassing centers (Cheb basin, Mariánské Lázně, and Karlovy Vary) with high CO2 flux and the same level of δ13C values, but different levels of 3He/ 4He ratios, have been identified. The studies have located the CO2 source and have investigated seismically induced changes in fluid characteristics on the basis of unique weekly sampling campaigns at selected locations. A seismically triggered release of crustal helium was confirmed by both monitoring campaigns. Finally, indications for a presently active magmatic process beneath the Cheb basin have been found. In contrast to volcanically active regions, magma accumulation in the study area takes place at the crust-mantle boundary and is not yet accompanied by heat transfer to the surface. Likewise, reactive magma-derived components are absent in the degassing fluids. The area of investigation has the potential to be a natural laboratory for fundamental studies of active geodynamic processes. The results of our fluid monitoring, including the stunning observation of mantle-derived free fluids marked by 3He/4He ratios within the subcontinental mantle range, are supported by geophysical findings from seismic studies and geologic indications. Copyright 2008 by the American Geophysical Union. Article 2008 English 15252027 10.1029/2007GC001921 Geochemistry, Geophysics, Geosystems 9 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-57549101480&doi=10.1029%2f2007GC001921&partnerID=40&md5=52fc58ebe685ae0151238fad624f7c10 Cited by: 54 Karin Bräuer Horst Kämpf Samuel Niedermann Gerhard Strauch Jiří Tesař article Fischer2008493 We present the pattern of seismic activity in the period between 2001 and 2007 for the Novä Kostel focal zone, which is recently the most active zone of the West-Bohemia/Vogtland earthquake swarm region. While the year 2001 was characterized by dying out of the 2000-swarm activity in the form of a few microswarms, almost no seismicity occurred in the period between 2002 and 2003. Since 2004 an elevated seismic activity occurs in the form of repeating microearthquake swarms. We used a relative location method to relate the hypocenter positions of the post-swarm activity to the geometry of the 2000-swarm cluster. We found that the activity has concentrated in several clusters, which have been repeatedly activated. Some clusters coincide with the position of the previous activity; the others have activated so far inactive deep segments at the southern edge of the Novä Kostel fault. Besides the shift of the hypocenters to the edges of the previously active area we observe a southward migration of the activity and an increase of maximum depths of earthquakes from 10 to 13 km. The waveform similarity analysis disclosed that some fault patches consist of only a single, repeatedly activated fault plane, while the others consist of multiple, differently oriented fault planes activated almost simultaneously. Most of the focal mechanisms are consistent with the geometry of hypocenters showing NNW-SSE trending steep fault planes with left-lateral strike-slip mechanisms and varying dip-slip component. © Institute of Geophysics of the ASCR, v.v.i 2008. Article 2008 English 00393169 10.1007/s11200-008-0034-y Studia Geophysica et Geodaetica 52 Springer New York 493 – 512 4 earthquake hypocenter; earthquake swarm; microearthquake; seismic migration; seismicity; strike-slip fault; waveform analysis https://www.scopus.com/inward/record.uri?eid=2-s2.0-57549117787&doi=10.1007%2fs11200-008-0034-y&partnerID=40&md5=467388ff248f37cae39cf937fd0e1676 Cited by: 40 T. Fischer J. Michálek article Horálek2008455 We summarise the results of seismological studies related to triggering mechanisms, driving forces and source processes of the West Bohemia/ Vogtland earthquake swarms with the aim to disclose the role of crustal fluids in the preparation, triggering and governing of the swarms. We present basic characteristics distinguishing earthquake swarms from tectonic mainshock-aftershock sequences and introduce existing earthquakes swarm models. From the statistical characteristics and time-space distribution of the foci we infer that self-organization is a peculiarity of West Bohemia/Vogtland swarms. We discuss possible causes of the foci migration in these swarms from the viewpoint of co-seismic and/or post-seismic stress changes and diffusion of the pressurized fluids, and we summarize hitherto published models of triggering the 2000-swarm. Attention is paid to the source mechanisms, particularly to their non-shear components. We consider possible causes of different source mechanisms of the 1997-and 2000-swarms and infer that pure shear processes controlled solely by the regional tectonic stress prevail in them, and that additional tensile forces may appear only at unfavourably oriented faults. On data from the fluid injection experiment at the HDR site Soultz (Alsace), we also show that earthquakes triggered by fluids can represent purely shear processes. Thus we conclude that increased pore pressure of crustal fluids in the region plays a key role in bringing the faults from the subcritical to critical state. The swarm activities are mainly driven by stress changes due to co-seismic and post-seismic slips, which considerably depend on the frictional conditions at the fault; crustal fluids keep the fault in a critical state. An open question still remains the cause of the repeatedly observed almost simultaneous occurrence of seismic activity in different focal zones in a wider area of West Bohemia/Vogtland. The analysis of the space-time relations of seismicity in the area between 1991 and 2007 revealed that during a significant part of this time span the seismicity was switching among distant focal zones. This indicates a common triggering force which might be the effect of an increase of crustal-fluid pore-pressure affecting a wider epicentral region. © Institute of Geophysics of the ASCR, v.v.i 2008. Review 2008 English 00393169 10.1007/s11200-008-0032-0 Studia Geophysica et Geodaetica 52 455 – 478 4 aftershock; crustal structure; earthquake epicenter; earthquake swarm; fluid; fluid injection; pore pressure; seismic source; seismicity; trigger mechanism https://www.scopus.com/inward/record.uri?eid=2-s2.0-57549113662&doi=10.1007%2fs11200-008-0032-0&partnerID=40&md5=a52f3b3acdc25ff9da58e13f4d7b779c Cited by: 68 J. Horálek T. Fischer article Korn2008479 A new network of permanently recording seismic stations in West Saxony has considerably improved detection threshold, location accuracy and depth determination in this seismically active region. Between 2001 and 2007 more than 900 events have been located. Seismicity mainly occurred along a band stretching north-south between Leipzig and Vogtland/NW Bohemia area with local magnitudes ranging between 0.8 and 2.8. Seismicity clearly delineates the Leipzig-Regensburg (L-R) fault zone striking N-S, and the Gera-Jachymov (G-J) fault zone striking roughly NNW-SSE. The hypocentral depths can be divided into two depth ranges, one at depths below 10 km, and a second at less than 10 km depth that only extends S-N from the Vogtland until the crossing between L-R and G-J fault zones. A small earthquake sequence that occurred near Werdau/ Zwickau in August 2006 at almost the same epicenters as an earlier sequence 1997/98 seems to confirm this finding: a relative localization of 15 events with the double-difference technique clearly reveals two distinct subclusters at about 6 and 12-14 km depth. With the improved station coverage 33 new fault plane solutions from events along the L-R fault zone north of the swarmquake area could be determined from P-polarities and P/S ratios. They do not differ significantly from solutions in the Vogtland/NW-Bohemia area and are mostly compatible with a N-S oriented fault plane. Strike slip mechanisms with or without a dip slip component dominate. © Institute of Geophysics of the ASCR, v.v.i 2008. Article 2008 English 00393169 10.1007/s11200-008-0033-z Studia Geophysica et Geodaetica 52 479 – 492 4 Central Europe; Eurasia; Europe; Germany; Saxony; earthquake epicenter; earthquake hypocenter; fault zone; seismicity; seismotectonics; source parameters; strike-slip fault https://www.scopus.com/inward/record.uri?eid=2-s2.0-57549090207&doi=10.1007%2fs11200-008-0033-z&partnerID=40&md5=864b7edeadad7a0f10f0f8f4cce6df3c Cited by: 13 M. Korn S. Funke S. Wendt article Bräuer2007 We present a study considering the systematics of gas and isotope compositions (3He/4He, δ13 CCO2, δ13 CCH4, δ 15N) of a permanent magmatic CO2 flux in the hydrothermal system of the spring "Wettinquelle" in Bad Brambach and their relation to the seismic activity beneath the western Eger rift. The gas and isotope compositions were monitored for more than 3 years. The time series includes periods before, during, and after a 4-month-long seismically active period from the end of August to the end of December 2000. Shifts due to admixture of crustal components were found for all monitored isotope ratios during and after the seismically active period. In case of helium and nitrogen, isotopic anomalies occurred already about 6 weeks before the beginning of the seismically active period, contemporaneous with a water level anomaly of the well VL4 near the Wettinquelle. On the one hand, preseismic deformations may be responsible for the observed isotope anomalies; on the other hand, coseismic fracturing processes in the surroundings of the hypocenters may play a role. Both effects produce greater permeability and result in the release of crustal fluids. The migration and admixture of these crustal components to the "permanent" upper mantle-derived fluid flux result in geochemical anomalies that persist for more than 2 years. The results of the detailed isotope monitoring have proven to be an important contribution to understand the geodynamic processes that may presently be going on in the region Vogtland/NW Bohemia. Copyright 2007 by the American Geophysical Union. Article 2007 English 21699313 10.1029/2006JB004404 Journal of Geophysical Research: Solid Earth 112 Blackwell Publishing Ltd 4 Central Europe; Eger; Eurasia; Europe; Heves; Hungary; coseismic process; fluid composition; geodynamics; hydrothermal system; isotopic composition; thermal spring https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250690764&doi=10.1029%2f2006JB004404&partnerID=40&md5=8eeb69f543fa0a54bc5845db364fbdeb Cited by: 33 Karin Bräuer Horst Kämpf Ulrich Koch Samuel Niedermann Gerhard Strauch article Plomerová2007675 We present the first results of a high-resolution teleseismic traveltime tomography and seismic anisotropy study of the lithosphere-asthenosphere system beneath the western Bohemian Massif. The initial high-resolution tomography down to a depth of 250 km did not image any columnar low-velocity anomaly which could be interpreted as a mantle plume anticipated beneath the Eger Rift, similar to recent findings of small plumes beneath the French Massif Central and the Eifel in Germany. Alternatively, we interpret the broad low-velocity anomaly beneath the Eger Rift by an upwelling of the lithosphere-asthenosphere transition. We also map lateral variations of seismic anisotropy of the mantle lithosphere from spatial variations of P-wave delay times and the shear wave splitting. Three major domains characterised by different orientations of seismic anisotropy correspond to the major tectonic units - Saxothuringian, Moldanubian and the Teplá-Barrandian - and their fabrics fit to those found in our previous studies of mantle anisotropy on large European scales. © 2007 The Authors Journal compilation © 2007 RAS. Article 2007 English 1365246X 10.1111/j.1365-246X.2007.03361.x Geophysical Journal International 169 675 – 682 2 Bohemian Massif; Central Europe; Eurasia; Europe; asthenosphere; lithosphere; P-wave; rift zone; seismic anisotropy; seismic tomography; teleseismic wave; travel time; upper mantle https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247251535&doi=10.1111%2fj.1365-246X.2007.03361.x&partnerID=40&md5=20f7392f25b4a6bbdfc24c9de5dee735 Cited by: 73; All Open Access, Bronze Open Access Jaroslava Plomerova Ulrich Achauer Vladislav Babuška Ludečk Vecsey article Vylita2007427 The first set of U-series ages of the hot-spring travertine from the world-famous Karlovy Vary Spa indicates repeated growth of the travertine accumulation followed by its erosion by the Teplá River. The obtained data are important as an estimate of minimum duration of thermal water circulation in Karlovy Vary and in understanding of the river valley evolution during the youngest geological history. The oldest 230Th/ 234U age data (230 ± 14 ka BP and 155 ± 7 ka BP) have been obtained for travertine relicts located 22 m above the present-day bottom of the valley. The extensive travertine accumulation located directly on the valley bottom was formed by gradual growth, particularly during the first half of the Weichselian period, between 100 and 50 ka BP. These data show that the valley bottom was at approximately the same elevation as it is today already during the Eemian interglacial. At the end of the Weichselian the central part of the travertine accumulation was downcut by river erosion. During Holocene the new deposition of travertine was concentrated in this wide trench, being likely repeatedly modified by river activity. The travertine accumulation started to be strongly influenced by humans since the Middle Ages. A significant part of it was quarried out for lime production. The accumulation was later covered by buildings, streets and the reinforced course of the Teplá River. © 2007 Gebrüder Borntraeger. Article 2007 English 03728854 10.1127/0372-8854/2007/0051-0427 Zeitschrift fur Geomorphologie 51 Schweizerbart Science Publishers 427 – 442 4 Central Europe; Czech Republic; Eurasia; Europe; Karlovarsky; Karlovy Vary; Tepla River; concentration (composition); dating method; Eemian; geochronology; Holocene; interglacial; landform evolution; thermal evolution; thermal spring; travertine https://www.scopus.com/inward/record.uri?eid=2-s2.0-38149108203&doi=10.1127%2f0372-8854%2f2007%2f0051-0427&partnerID=40&md5=1d27a61705c4332ffaaf73be58fa26f5 Cited by: 24 Tomáš Vylita Karel Žák Václav Cílek Helena Hercman Lucie Mikšíková article Geissler200733 New petrological and geochemical data of upper mantle and lower crustal xenoliths from a Quaternary tephra deposit in Mýtina, Czech Republic, are discussed in the frame of previous geophysical results (receiver functions, reflection seismology) of the western Eger/Ohře Rift area. The Vogtland/NW Bohemia region is well known for intraplate earthquake swarms, which are usually associated with volcanic activity. As previously reported, 3He/4He data of CO2 emissions in mofettes and mineral-water springs point at ongoing magmatic processes in this area. Using teleseismic P receiver functions, an approximately 40-km-wide Moho updoming (from 31 to 27 km) and indications for a seismic discontinuity at 50 to 60 km depth were observed beneath the active CO2-degassing field. The studied xenolith suite probes a lithospheric profile within the structural and gas geochemical anomaly field of the western Eger Rift. With regard to texture, composition, p-T estimates and origin, five xenolith groups can be discriminated. Upper crustal xenoliths (quartzites, phyllites, mica schists) resemble crystalline country rocks at surface. One noritic xenolith (6 kbar, 800 °C) could represent a sample of the lower crust. Clinopyroxenites and hornblendites probably represent cumulates of the nephelinitic magma or fragments of magmatic veins. Porous wehrlites and one hornblende peridotite xenolith reflect a metasomatied upper mantle. Megacrysts of Ti-rich amphibole, olivine, clinopyroxene, and phlogopite could be fragments of pegmatitic veins or high-pressure phenocrysts. Most of the ultramafic nodules (xenoliths and megacrysts) formed at pressures between 6 and 11 kbar (22 to 38 km depth), at temperatures well above regional geotherms of the Bohemian Massif calculated from surface heat flow studies. Orthopyroxene-bearing spinel-lherzolite xenoliths were not observed. Our petrographical, geochemical, and thermobarometric results indicate a lithospheric mantle strongly altered by magmatic processes. This metasomatism can cause slower than typical uppermost-mantle seismic velocities in a greater area and might help to explain observed seismic anomalies. © 2006 Elsevier B.V. All rights reserved. Article 2007 English 03770273 10.1016/j.jvolgeores.2006.06.011 Journal of Volcanology and Geothermal Research 159 33 – 69 1-3 Bohemia; Central Europe; Czech Republic; Eger; Eurasia; Europe; Germany; Heves; Hungary; Vogtland; Barometers; Earthquakes; Geothermal fields; Lithology; Petrology; Seismology; Thermometers; Volcanic rocks; earthquake swarm; lithosphere; mantle chemistry; Moho; petrology; Quaternary; seismic velocity; teleseismic wave; tephra; upper mantle; xenolith; Earthquake swarm region; Lithosphere; Quaternary volcanism; Seismic structure; Volcanoes https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845566745&doi=10.1016%2fj.jvolgeores.2006.06.011&partnerID=40&md5=b53cd442f76ed88dee05c5cd32a6274c Cited by: 30 W.H. Geissler H. Kämpf W. Seifert P. Dulski article Brückl2007 Alp01 and Alp02 are the longest profiles recorded during ALP 2002, a large international seismic refraction and wide-angle reflection experiment undertaken in the Eastern Alps in 2002. Alp01 crosses the Alpine orogen from north to south, thus providing a cross section mainly affected by the collision between Europe and the Adriatic microplate. Alp02 extends from the Eastern Alps to the Pannonian basin, supplying evidence on the relation between Alpine crustal structure and tectonic escape to the Pannonian basin. During this experiment, 363 single-channel recorders were deployed along these profiles with an average spacing of 3.2 km. Recordings from 20 inline shots were used in this study. Two-dimensional forward modeling using interactive ray-tracing techniques produced detailed P wave velocity models that contain many features of tectonic significance. Along Alp01, the European Moho dips generally to the south and reaches a maximum depth of 47 km below the transition from the Eastern to the Southern Alps. The Adriatic Moho continues further south at a significantly shallower depth. Moho topography and a prominent south-dipping mantle reflector in the Alpine area support the idea of southward subduction of the European lithosphere below the Adriatic microplate. The most prominent tectonic feature on the Alp02 profile is a vertical step of the Moho at the transition between the Alpine and Pannonian domains, suggesting the existence of a separate Pannonian plate fragment. The development of the Pannonian fragment is interpreted to be a consequence of crustal thinning due to tectonic escape from the Alpine collision area to the Pannonian basin. Copyright 2007 by the American Geophysical Union. Article 2007 English 21699313 10.1029/2006JB004687 Journal of Geophysical Research: Solid Earth 112 Blackwell Publishing Ltd 6 Alps; Eastern Alps; Eurasia; Europe; Pannonian Basin; crustal structure; forward modeling; Moho; ray tracing; seismic reflection; seismic refraction; seismic velocity; seismotectonics https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548448833&doi=10.1029%2f2006JB004687&partnerID=40&md5=ccad174c81a87a00551368f4eb8e5dfa Cited by: 103 Ewald Brückl Florian Bleibinhaus Andrej Gosar Marek Grad Aleksander Guterch Pavla Hrubcová G. Randy Keller Mariusz Majdański Franjo Šumanovac Timo Tiira Jukka Yliniemi Endre Hegedus Hans Thybo article IbsvonSeht2006197 A seismicity and stress field analysis of a region in NE Bavaria reveals a complex picture of seismic dislocation. The magnitudes are generally low, the strongest event recorded had a magnitude of 2.3. In the southern part of the area investigated, earthquakes occur very rarely. During the observation period of approximately four years, only four events, two of them forming a doublet, were recorded. Hypocentral depths in the southern part are considerably great (15 to 17 km) and indicate a mafic lower crust. The seismicity of the Marktredwitz area, located in the western extension of the Eger rift, is dominated by earthquake swarms that are strongly clustered in space and time. The swarms occurred at depths between 10 and 14 km. Precise relative relocations show clear planar arrangements of the hypocentres and enable to identify the orientation of active fault planes. A comparison of the structural and geomorphological settings reveals major similarities in the occurrence of earthquake swarms compared to the situation in the bordering Vogtland/NW-Bohemia swarm area. Focal mechanisms cover a wide range of faulting styles. Normal fault, strike slip and reverse fault mechanisms as well as movements along sub-horizontal planes were found. The focal mechanisms were used to invert for the stress field. The inversion results reveal an ambiguity for the state of stress in the area of investigation and allow two different interpretations: A clockwise rotation of the stress field from North to South as well as a predominance of two slightly different stress regimes are possibilities. © Springer Science+Business Media, Inc. 2006. Article 2006 English 13834649 10.1007/s10950-005-9008-5 Journal of Seismology 10 197 – 211 2 Bavaria; Central Europe; Eurasia; Europe; Germany; earthquake magnitude; earthquake swarm; focal mechanism; seismicity; stress field https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748062335&doi=10.1007%2fs10950-005-9008-5&partnerID=40&md5=5258095a8b9d6fd827a8c5041aabbe8b Cited by: 9 M. Ibs-von Seht T. Plenefisch E. Schmedes article Heuer2006 Detailed images of the lithosphere beneath the western Bohemian Massif were obtained by analysis of more than 8500 P receiver functions. At the intersection of Regensburg-Leipzig-Rostock zone and Eger Rift, crustal thickness decreases to 26 km from approx. 31 km in the surroundings. The receiver functions display a positive phase at about 6 s delay time and a strong negative phase at 7 to 8 s, which coincides with an area of Moho updoming, CO2 mantle-derived degassing and earthquake swarm activity. These phases can be modeled by a velocity increase at 50 km and a velocity decrease at 65 km depth. The velocity decrease, observed over an area of 5300 km2, gives evidence for local asthenospheric updoming and/or a confined body of partial melt, which might be the cause for high CO2 mantle fluid flow and earthquake swarm activity in this recently nonvolcanic, intracontinental rift area. Copyright 2006 by the American Geophysical Union. Article 2006 English 00948276 10.1029/2005GL025158 Geophysical Research Letters 33 5 Bohemian Massif; Central Europe; Eurasia; Europe; Carbon dioxide; Degassing; Earthquakes; Flow of fluids; Tectonics; asthenosphere; crustal thickness; earthquake swarm; fluid flow; imaging method; mantle process; Asthenospheric updoming; Carbon dioxide mantle-derived degassing; Earthquake swarm activity; Seismology https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646363323&doi=10.1029%2f2005GL025158&partnerID=40&md5=51c682b149950f1a934424e6a07e7e81 Cited by: 57; All Open Access, Bronze Open Access B. Heuer W.H. Geissler R. Kind H. Kämpf article Hrubcová20051 The deep structure of the Bohemian Massif (BM), the largest stable outcrop of Var scan rocks in central Europe, was studied using the data of the international seismic refraction experiment Central European Lithospheric Experiment Based on Refraction (CELEBRATION) 2000. The data were interpreted by seismic tomographic inversion and by two-dimensional (2-D) trial-and-error forward modeling of P and S waves. Additional constraint on crustal structure was given by amplitude modeling using the reflectivity method and gravity modeling. Though consolidated, the BM can be subdivided into several tectonic units separated by faults, shear zones, or thrusts reflecting varying influence of the Cadomian and Variscan orogeneses: the Saxothuringian, Barrandian, Moldanubian, and Moravian. Velocity models determine three types of crust-mantle transition in the BM reflecting variable crustal thickness and delimiting contacts of tectonic units in depth. The NW area, the Saxothuringian, has a highly reflective lower crustal layer above Moho with a strong velocity contrast at the top of this layer. This reflective laminated lower crust reaches depths of 26-35 km and is characteristic for the Saxothuringian unit, which was subject to eastward subduction. The Moldanubian in the central part is characterized by the deepest (39 km) and the most pronounced Moho within the whole BM with a strong velocity contrast 6.9-8.1 kin s-1. A thick crust-mantle transition zone in the SE, with velocity increase from 6.8 to 7.8 km s-1 over the depth range of 23-40 km, seems to be the characteristic feature of the Moravian overthrusted by the Moldanubian during Variscan collision. Copyright 2005 by the American Geophysical Union. Article 2005 English 21699313 10.1029/2004JB003080 Journal of Geophysical Research: Solid Earth 110 Blackwell Publishing Ltd 1 – 21 11 Bohemian Massif; Central Europe; Eurasia; Europe; crustal structure; mantle structure; seismic tomography https://www.scopus.com/inward/record.uri?eid=2-s2.0-30144441019&doi=10.1029%2f2004JB003080&partnerID=40&md5=4a6b604a4cc097433310f865dae0e83e Cited by: 129 Pavla Hrubcová P. Środa A. Špičák A. Guterch M. Grad G.R. Keller E. Brueckl H. Thybo article Špičák200544 2005 English 18168957 10.5194/sd-1-44-2005 Scientific Drilling 1 Copernicus GmbH 44-45 Geophysical Institute of the Academy of Sciences of the Czech Republic, Bocni II/1401 14131, Prague 4, Czech Republic; GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, 14473, Germany Energy resources; Mechanical engineering, Drilling https://www.scopus.com/inward/record.uri?eid=2-s2.0-57649207115&doi=10.5194%2fsd-1-44-2005&partnerID=40&md5=d1a19e7add4f9d8bab45a03a71d0cc73 cited By 6 A. Špičák A. Förster B. Horsfield article Bräuer20051 We present new 3He/4He data of CO2-rich gas exhalations of three presently nonvolcanic areas in Europe. The 3He/4He ratios from the Cheb basin (Czech Republic) are clearly higher than data obtained ten years ago, whereas the 3He/4He ratios from the other areas (Laacher See/Germany and Mariánské Lázně/CR) have remained nearly constant. No other locality showing such high 3He/4He ratios in free gases supplied by continental mantle degassing is known in the European Cenozoic rift system. At the northeastern edge of the Cheb basin swarm earthquakes repeatedly occur. In the context of contemporaneous periods of seismicity the increased 3He/4He ratios are interpreted as the first geochemical evidence for ascending mantle-derived melt beneath the Cheb basin, which is related to the triggering of earthquake swarms. Copyright 2005 by the American Geophysical Union. Article 2005 English 00948276 10.1029/2004GL022205 Geophysical Research Letters 32 American Geophysical Union 1 – 4 8 Central Europe; Cheb Basin; Czech Republic; Eastern Hemisphere; Eurasia; Europe; World; Catchments; Degassing; Earthquakes; Helium; Europe; Mantle; Nonvolcanic areas; Rifts; mantle plume; Geophysics https://www.scopus.com/inward/record.uri?eid=2-s2.0-22944484430&doi=10.1029%2f2004GL022205&partnerID=40&md5=0c1993ec7c6739d8e67323bf678690fc Cited by: 62 Karin Bräuer Horst Kämpf Samuel Niedermann Gerhard Strauch article Geissler20051 P-SV conversions provide new insights into the lithosphere of the western Eger (Ohře) Rift, a presently active CO2 emanation area, Quaternary volcanic field, and earthquake swarm region in central Europe. Gas and isotope (He and C) mapping of free gas phases in mineral springs and mofettes proved the origin Of CO2-dominated gases from a subcrustal magmatic fluid reservoir. Analyzing teleseismic data from several seismic networks in the western Bohemian Massif the source region of these gases was investigated Moho Ps conversions have 3 to 4.5 s delay. Crustal thicknesses vary between 27 and 38 km; vp/vs ratios vary between 1.63 and 1.81. Beneath the western Eger Rift an approximately 40 km wide Moho updoming up to 27 km exists. Locally observed weak conversions indicate a complex Moho transition zone in this area. A local "6 s phase" possibly originates at a discontinuity in approximately 50 to 60 km depth or may represent multiples from velocity inversions at the base of the upper crust. Moho updoming and the distribution of the "6 s phase" coincide with the CO2 degassing fields and the positions of Quaternary volcanoes at the surface. We hypothesize the release of CO2-dominated fluid/magma from isolated melt reservoirs in the depth range of 60 to 30 km, separation of CO2 from the melt at 29 to 21 km depths, and CO2 transport through the crust. The geophysical indications may point to presently active magmatic underplating beneath the study area, supporting the results of gas geochemical and isotope investigations. This is the first attempt that combines seismic and gas geochemical data for a tectonic model. Our model may be transferable to other continental rift areas worldwide. Copyright 2005 by the American Geophysical Union. Article 2005 English 02787407 10.1029/2004TC001672 Tectonics 24 1 – 23 5 Central Europe; Eurasia; Europe; Ohre River; carbon dioxide; lithospheric structure; seismic velocity; upper mantle https://www.scopus.com/inward/record.uri?eid=2-s2.0-23344445479&doi=10.1029%2f2004TC001672&partnerID=40&md5=85dc499b91d4d419a3f34a186ee050ec Cited by: 99; All Open Access, Bronze Open Access Wolfram H. Geissler Horst Kämpf Rainer Kind Karin Bräuer Klaus Klinge Thomas Plenefisch Josef Horálek Jan Zedník Vladimir Nehybka