This file was created by the TYPO3 extension publications --- Timezone: CEST Creation date: 2026-04-23 Creation time: 15:26:18 --- Number of references 19 article Mngadi202533 Article 2025 10.17159/2411-9717/3445/2025 Journal of the Southern African Institute of Mining and Metallurgy 125 33 – 42 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85217887529&doi=10.17159%2f2411-9717%2f3445%2f2025&partnerID=40&md5=5d60f228e9eba0d26e9f3c13f825fde8 Cited by: 0; All Open Access, Gold Open Access S.B. Mngadi M.S.D. Manzi N.Z. Nkosi R.J. Durrheim H. Ogasawara Y. Yabe article Nisson2024 Article 2024 10.1093/ismeco/ycae138 ISME Communications 4 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-105009719003&doi=10.1093%2fismeco%2fycae138&partnerID=40&md5=66be5f2b6107918f60e24c8869872a0e Cited by: 1; All Open Access, Gold Open Access, Green Open Access Devan M. Nisson Thomas L. Kieft Julio Castillo Scott M. Perl Tullis C. Onstott article Ogasawara2024817 Article 2024 10.2320/matertrans.MT-Z2024004 Materials Transactions 65 817 – 823 7 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85197348178&doi=10.2320%2fmatertrans.MT-Z2024004&partnerID=40&md5=e3d474d90888c376a38c81426fb3c385 Cited by: 0; All Open Access, Gold Open Access Hiroshi Ogasawara Yoshihiro Mima Akimasa Ishida Siyanda Mngadi Mitsuya Higashi Yasuo Yabe Akio Funato Takatoshi Ito Masao Nakatani Raymond Durrheim article NISSON202365 Geochemical and isotopic fluid signatures from a 2.9–3.2 km deep, 45–55 °C temperature, hypersaline brine from Moab Khotsong gold and uranium mine in the Witwatersrand Basin of South Africa were combined with radiolytic and water–rock isotopic exchange models to delineate brine evolution over geologic time, and to explore brine conditions for habitability. The Moab Khotsong brines were hypersaline (Ca-Na-Cl) with 215–246 g/L TDS, and Cl− concentrations up to 4 mol/L suggesting their position as a hypersaline end-member significantly more saline than any previously sampled Witwatersrand Basin fluids. The brines revealed low DIC (∼0.266–∼1.07 mmol/L) with high (∼8.49–∼23.6 mmol/L) DOC pools, and several reduced gaseous species (up to 46 % by volume H2) despite microoxic conditions (Eh = 135–161 mV). Alpha particle radiolysis of water to H2, H2O2, and O2 along with anhydrous-silicate-to-clay alteration reactions predicted 4 mol/L Cl− brine concentration and deuterium enrichment in the fracture waters over a period > 1.00 Ga, consistent with previously reported 40Ar noble gas-derived residence times of 1.20 Ga for this system. In addition, radiolytic production of 7–26 nmol/(L × yr) H2, 3–11 nmol/(L × yr) O2, and 1–8 nmol/(L × yr) H2O2 was predicted for 1–100μ g/g 238U dosage scenarios, supporting radiolysis as a significant source of H2 and oxidant species to deep brines over time that are available to a low biomass system (102–103 cells/mL). The host rock lithology was predominately Archaean quartzite, with minerals exposed on fracture surfaces that included calcite, pyrite, and chlorite. Signatures of δ18Ocalcite, δ13Ccalcite, Δ33Spyrite, δ34Spyrite and 87Sr/86Sr obtained from secondary ion mass spectrometry (SIMS) microanalyses suggest several discrete fluid events as the basin cooled from peak greenschist conditions to equilibrium with present-day brine temperatures. The brine physiochemistry, geochemistry, and cellular abundances were significantly different from those of a younger, shallower, low salinity dolomitic fluid in the same mine, and both were different from the mine service water. These results indicate the discovery of one of few long-isolated systems that supports subsurface brine formation via extended water–rock interaction, and an example of a subsurface brine system where abiotic geochemistry may support a low biomass microbial community. 2023 0016-7037 https://doi.org/10.1016/j.gca.2022.11.015 Geochimica et Cosmochimica Acta 340 65-84 Groundwater, Brine, Radiolysis, Isotope geochemistry, Deep biosphere https://www.sciencedirect.com/science/article/pii/S0016703722006226 D.M. Nisson T.L. Kieft H. Drake O. Warr B. Sherwood Lollar H. Ogasawara S.M. Perl B.M. Friefeld J. Castillo M.J. Whitehouse E. Kooijman T.C. Onstott article Nisson20236163 Investigations of abiotic and biotic contributions to dissolved organic carbon (DOC) are required to constrain microbial habitability in continental subsurface fluids. Here we investigate a large (101-283 mg C/L) DOC pool in an ancient (>1Ga), high temperature (45-55 °C), low biomass (102-104 cells/mL), and deep (3.2 km) brine from an uranium-enriched South African gold mine. Excitation-emission matrices (EEMs), negative electrospray ionization (-ESI) 21 tesla Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), and amino acid analyses suggest the brine DOC is primarily radiolytically oxidized kerogen-rich shales or reefs, methane and ethane, with trace amounts of C3-C6 hydrocarbons and organic sulfides. δ2H and δ13C of C1-C3 hydrocarbons are consistent with abiotic origins. These findings suggest water-rock processes control redox and C cycling, helping support a meagre, slow biosphere over geologic time. A radiolytic-driven, habitable brine may signal similar settings are good targets in the search for life beyond Earth. © 2023. Springer Nature Limited. Article 2023 English 20411723 10.1038/s41467-023-41900-8 Nature communications 14 NLM (Medline) 6163 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85173033706&doi=10.1038%2fs41467-023-41900-8&partnerID=40&md5=44971859742f636e33b15fa70f7022fc Cited by: 0; All Open Access, Gold Open Access Devan M. Nisson Clifford C. Walters Martha L. Chacón-Patiño Chad R. Weisbrod Thomas L. Kieft Barbara Sherwood Lollar Oliver Warr Julio Castillo Scott M. Perl Errol D. Cason Barry M. Freifeld Tullis C. Onstott article Nkosi2022 Petrophysical properties of cylindrical core specimens from three boreholes from the International Continental Scientific Drilling Program, the DSeis project, measured at ambient pressure and room temperature conditions in various laboratories are presented and compared with downhole petrophysical data (sonic and density). The measured properties are from sixty-six rock specimens constituting metasediments, metabasalts and intrusives. Seismic velocities were measured using 0.5 MHz P- and S-wave transducers. To investigate the source of seismic reflectivity observed on the 2D legacy seismic data, we computed synthetic seismograms for adjacent rock units using downhole petrophysical data and compared them with seismic reflections from the reflection seismic profile. The experimental measurements show that the metasediments exhibit lower bulk densities and seismic velocities than the metabasalts and intrusive specimens. The porosity was found to be less than 2% for all the samples. No clear trends emerge when the Poisson's ratio is plotted against the P-wave velocities and porosities of the samples. A positive relationship is observed between the bulk modulus and P-wave velocities of the rock samples. The highest calculated reflection coefficients (RC) are associated with the metasediment-intrusive interfaces in all three boreholes. The intrusive-metabasalt and the metasediment-metabasalt interfaces exhibit low RC. Synthetic seismograms reveal strong reflections that coincide with high RC calculated using the bulk density and velocity data. The synthetic seismograms also revealed additional strong reflections that were not identified using the reflection coefficients calculated from the rock specimens, due to core loss in some lithological units. Successful correlations are carried out between the synthetic seismic data and the real seismic data, enabling us to correlate the stratigraphic sequence drilled in the boreholes to the seismic reflections observed on the legacy 2D reflection seismic data. © 2022 Elsevier Ltd Article 2022 English 13651609 10.1016/j.ijrmms.2022.105082 International Journal of Rock Mechanics and Mining Sciences 155 Elsevier Ltd 105082 School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa; Council for Scientific and Industrial Research, Cnr Carlow and Rustenburg Rd, Auckland Park, Johannesburg, South Africa; Ritsumeikan University, Kusatsu, Japan; ETH, Zurich, Switzerland; Moab Khotsong mine, South Africa; Princeton University, United States South Africa; Acoustic wave velocity; Boreholes; Earthquakes; Geophysical prospecting; Infill drilling; Petrophysics; Porosity; Reflection; Rocks; Seismic response; Seismic waves; Shear waves; Stratigraphy; Wave propagation; Well logging; Downholes; Metabasalts; Mining induced earthquake; P-wave velocity; Petrophysical datum; S-wave velocity; Seismic datas; Seismic reflectivity; Sonic logs; Synthetic seismogram; gold mine; mining-induced seismicity; P-wave; physical property; S-wave; seismic reflection; seismic velocity; seismic zone; seismogram; ultrasonics; Lithology https://www.scopus.com/inward/record.uri?eid=2-s2.0-85130462900&doi=10.1016%2fj.ijrmms.2022.105082&partnerID=40&md5=64b73abe4e5ddfe9969bffc149386509 Cited by: 3; All Open Access, Bronze Open Access Nomqhele Z. Nkosi Musa S.D. Manzi Michael Westgate Dave Roberts Raymond J. Durrheim Hiroshi Ogasawara Martin Ziegler Michael Rickenbacher Bennie Liebenberg Tullis C. Onstott article Yabe20221679 In December 2007, an Mw2.2 earthquake occurred in a gabbroic dike at 3.3 km depth in a deep gold mine in South Africa. The fore- and aftershock activity was analyzed in an effort to understand the preparation and generation processes of earthquakes; these findings have already been published. The present paper focuses on the stress state in the source region of the mainshock. A 90-m-long borehole across the mainshock fault was drilled ~ 1.5 years after the mainshock and logged by an optical televiewer. The fault can be identified by severe damage to the borehole wall at the point where the borehole intersected the aftershock cluster. Except for a 10-m section in the hanging wall of the fault, borehole cores were fully recovered. Borehole breakout (BO) and core disking (CD) were found to occur. Two stress measurement techniques [Deformation Rate Analysis (DRA) and Diametrical Core Deformation Analysis (DCDA)] were applied to the borehole cores. By combining their results with occurrence criteria for BO and CD, the principal stress state in the source region of the mainshock was determined. The principal directions in the hanging wall of the fault were nearly identical to the virgin stress state, while it was significantly disturbed in the footwall. The vertical stresses were 106 MPa and 40 MPa in the hanging wall and footwall, respectively. The significant difference in the vertical stress between the two sides of the fault can be explained by the stress redistribution associated with a nonuniform slip on a nonplanar fault. © 2022, The Author(s). 2022 English 00334553 10.1007/s00024-022-02999-w Pure and Applied Geophysics 179 Birkhauser 1679-1700 Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, 6-6 Aramaki aza Aoba, Aoba-ku, Miyagi, Sendai, 980-8579, Japan; AngloGold Ashanti, Gauteng, South Africa; School of Mining Engineering, University of the Witwatersrand, Gauteng, Johannesburg, South Africa; College of Science and Engineering, Ritsumeikan University, Shiga, Kusatsu, Japan; Institute of Fluid Science, Tohoku University, Miyagi, Sendai, Japan; Fukada Geological Institute, Tokyo, Japan; Earthquake Research Institute, The University of Tokyo, Tokyo, Japan; Disaster Prevention Research Institute, Kyoto University, Kyoto, Uji, Japan; School of Geoscience, University of the Witwatersrand, Johannesburg, South Africa; Kokusai Kogyo Co., Ltd, Chiyoda, Tokyo, Japan; SibanyeStillwater, Carletonville, South Africa; Rock Mechanics Laboratory CC, Gauteng, Johannesburg, South Africa 5 Deformation; Earthquakes; Faulting; Gold mines; Infill drilling, Deep mine in south africa; Deep-mines; Deformation analysis; Deformation rate analyse; Deformation rate analysis; Diametrical core deformation analyse; Drilling intersecting a seismogenic fault; Earthquake source; Seismogenic faults; Source region; South Africa; Stress in earthquake source region, Boreholes, aftershock; borehole stability; deformation mechanism; drilling; earthquake event; earthquake magnitude; gabbro; gold mine, South Africa https://www.scopus.com/inward/record.uri?eid=2-s2.0-85127564479&doi=10.1007%2fs00024-022-02999-w&partnerID=40&md5=7d37fad5df28e36d30386f2b78c4917d cited By 0 Y. Yabe S. Abe G. Hofmann D. Roberts H. Yilmaz H. Ogasawara T. Ito A. Funato M. Nakatani M. Naoi article https://doi.org/10.1029/2022GL098745 Abstract Cores recovered during the International Continental Scientific Drilling Program project “Drilling into Seismogenic zones of M2.0 to M5.5 earthquakes in deep South African Gold Mines” include fault breccia from within the aftershock cloud of the 2014 Orkney earthquake (M5.5). The breccia and surrounding intrusive rocks, probably lamprophyres rich in talc, biotite, calcite, and amphibole, had high magnetic susceptibilities owing to the presence of magnetite. All of these characteristics can be attributed to fluid-related alteration. Both the breccia and the lamprophyres had low friction coefficients and showed evidence of velocity strengthening, which is inconsistent with the occurrence of earthquakes. Variable amounts of talc, biotite, calcite, and amphibole within the lamprophyres might have produced complex frictional properties and spatial heterogeneity of fault stability. The altered lamprophyres may be the host rocks of the 2014 Orkney earthquake, but frictional complexity may have governed the magnitudes of the main- and aftershocks and their distributions. 2022 https://doi.org/10.1029/2022GL098745 Geophysical Research Letters 49 e2022GL098745 14 earthquake, fault drilling, lamprophyre https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2022GL098745 e2022GL098745 2022GL098745 T. Miyamoto T. Hirono Y. Yokoyama S. Kaneki Y. Yamamoto T. Ishikawa A. Tsuchiyama I. Katayama Y. Yabe R. J. Durrheim H. Ogasawara article Ogasawara2022259 Article 2022 10.2472/jsms.71.259 Zairyo/Journal of the Society of Materials Science, Japan 71 259 – 264 3 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85128490409&doi=10.2472%2fjsms.71.259&partnerID=40&md5=672ad2365b3e3320766b2ff4531bcf94 Cited by: 0; All Open Access, Gold Open Access Hiroshi Ogasawara Yoshihiro Mima Akimasa Ishida Siyanda Mngadi Mitsuya Higashi Yasuo Yabe Akio Funato Takatoshi Ito Masao Nakatani Raymond Durrheim article Warr2022 Deep within the Precambrian basement rocks of the Earth, groundwaters can sustain subsurface microbial communities, and are targets of investigation both for geologic storage of carbon and/or nuclear waste, and for new reservoirs of rapidly depleting resources of helium. Noble gas-derived residence times have revealed deep hydrological settings where groundwaters are preserved on millions to billion-year timescales. Here we report groundwaters enriched in the highest concentrations of radiogenic products yet discovered in fluids, with an associated 86Kr excess in the free fluid, and residence times >1 billion years. This brine, from a South African gold mine 3 km below surface, demonstrates that ancient groundwaters preserved in the deep continental crust on billion-year geologic timescales may be more widespread than previously understood. The findings have implications beyond Earth, where on rocky planets such as Mars, subsurface water may persist on long timescales despite surface conditions that no longer provide a habitable zone. © 2022, The Author(s). 2022 English 20411723 10.1038/s41467-022-31412-2 Nature Communications 13 Nature Research Department of Earth Sciences, University of Toronto, Toronto, ON M5S 3B1, Canada; Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, United Kingdom; Department of Geosciences, Princeton University, Princeton, NJ 08544, United States; Biology Department, New Mexico Institute of Mining and Technology, Socorro, NM 87801, United States; IPGP, Sorbonne Paris Cité, 1 rue Jussieu, Paris, 75005, France 1 ground water; helium; helium 4; inert gas; krypton 86; neon; radioisotope; unclassified drug; uranium; xenon; xenon 136; inert gas, basement rock; concentration (composition); groundwater resource; helium; microbial community; Precambrian, air pollution; Article; astronomy; chemical composition; concentration (parameter); controlled study; geological time; gold mining; hydrosphere; Precambrian; sediment; South Africa; surface property; water residence time; water supply; geology; microflora, South Africa, Earth, Planet; Geology; Groundwater; Microbiota; Noble Gases https://www.scopus.com/inward/record.uri?eid=2-s2.0-85133137290&doi=10.1038%2fs41467-022-31412-2&partnerID=40&md5=6b3c0e403955ab1b367bf965edb44c4e cited By 2 O. Warr C.J. Ballentine T.C. Onstott D.M. Nisson T.L. Kieft D.J. Hillegonds B. Sherwood Lollar article MNGADI2021104454 The presence of fault gouge and the generation of wear material between two sliding rock surfaces plays a critical role in slip weakening and propagation of ruptures along underground brittle shear fractures forming ahead of tabular excavations in deep and high stress gold mining. We performed two types of friction experiments: one with a fault gouge layer between two sliding surfaces, and the other without a fault gouge layer ‘rock-on-rock’, both under room dry conditions at slip velocities ranging from ~1.0 mm/s to 1200 mm/s. These friction experiments revealed a remarkable difference in the frictional weakening behaviour, e.g., rock-on-rock friction experiments show weakening behaviour at lower slip velocity (~5 mm/s) and generally has lower frictional strength than those with the intervening fault gouge between sliding surfaces. This study shows that the existence of the fault gouge layer between sliding rock surfaces delays the onset of fault weakening (i.e., slip weakening displacement of gouge layer experiments is larger compared to rock-on-rock experiments). It is proposed that flash heating may be the main active weakening mechanism within both our gouge and rock-on-rock experiments, and provides a feasible account for the observed weakening. The observed slip weakening displacement (Dc) differences may be attributed to the presence of a gouge layer between sliding surfaces, which has many more contacts during sliding compared to rock-on-rock experiments, thus reducing the average slip velocity per contact, consequently, the potential for activation of flash heating which delays the onset of weakening. Here we suggest that we may be able to describe brittle shear fracture rupture propagation process along underground brittle shear zones by conducting low, intermediate and high slip velocity friction experiments with and without an intervening fault gouge between sliding rock surfaces. These findings should have important implications for the modelling of rupture propagation processes in underground shear zones, a phenomenon that influences the severity of rockbursts, and hence the safety of mine workers and mining operations. 2021 1365-1609 https://doi.org/10.1016/j.ijrmms.2020.104454 International Journal of Rock Mechanics and Mining Sciences 137 104454 Shear zones, Brittle shear fracture, Rupture propagation, Severity of rockbursts, Slip velocity friction experiments, Fault weakening behaviour https://www.sciencedirect.com/science/article/pii/S1365160920308236 S.B. Mngadi A. Tsutsumi Y. Onoe M.S.D. Manzi R.J. Durrheim Y. Yabe H. Ogasawara S. Kaneki N. Wechsler A.K. Ward M. Naoi H. Moriya M. Nakatani inproceedings 1952_28_Ogasawara In 2014, a M5.5 earthquake ruptured the range of depths between 3.5 km and 7 km near Orkney, South Africa. The main and aftershocks were very well monitored in the nearfield by dense, surface, strong motion meters and a dense underground seismic network in the deep gold mines. The mechanism of this M5.5 earthquake was left-lateral strike-slip faulting, differing from typical mining-induced earthquakes with normal-faulting mechanisms on the mining horizons shallower than 3.5 km depth. To understand why such an unusual event took place, the aftershock zone was probed by full-core NQ drilling during 2017-2018, with a total length of about 1.6 km, followed by in-hole geophysical logging, core logging, core testing, and monitoring in the drilled holes. These holes also presented a rare opportunity to investigate deep life. In addition, seismogenic zones of M2–M3 earthquakes were probed on mine horizons that were also very well monitored by acoustic emission networks. This paper reviews the early results of the project. 2019 10.36487/ACG_rep/1952_28_Ogasawara Deep Mining 2019: Proceedings of the Ninth International Conference on Deep and High Stress Mining The Southern African Institute of Mining and Metallurgy Joughin W 375-384 https://papers.acg.uwa.edu.au/p/1952_28_Ogasawara/ H Ogasawara B Liebenberg M Rickenbacher M Ziegler H Esterhuizen TC Onstott MSD Durrheim S Mngadi Y Yabe S Kaneki E Cason J-G Vermeuren E Heerden T Wiersberg M Zimmer C Kujawa R Conze G Aswegen N Wechsler AK Ward S Enslin S Tau MS Bucibo article Manzi201989 Article 2019 10.3997/1365-2397.n0050 First Break 37 89 – 96 8 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85072603317&doi=10.3997%2f1365-2397.n0050&partnerID=40&md5=2ccfb03198ed221ea3ad5ce7a6265aaf Cited by: 19 Musa Manzi Alireza Malehmir Raymond Durrheim article Mngadi201979 Article 2019 10.1016/j.ijrmms.2018.10.003 International Journal of Rock Mechanics and Mining Sciences 114 79 – 91 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059346741&doi=10.1016%2fj.ijrmms.2018.10.003&partnerID=40&md5=91e21c98f3e1dbe76a089d1958554ddc Cited by: 24 S.B. Mngadi R.J. Durrheim M.S.D. Manzi H. Ogasawara Y. Yabe H. Yilmaz N. Wechsler G. Van Aswegen D. Roberts A.K. Ward M. Naoi H. Moriya M. Nakatani A. Ishida SATREPS Team ICDP DSeis Team conference Ogasawara201939 Conference paper 2019 10.1201/9780429327933-5 Rock Dynamics Summit - Proceedings of the 2019 Rock Dynamics Summit, RDS 2019 39 – 44 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091657747&doi=10.1201%2f9780429327933-5&partnerID=40&md5=a3569cec87104380e609cfe6919ba7a0 Cited by: 0 H. Ogasawara A. Ishida K. Sugimura Y. Yabe S. Abe T. Ito A. Funato H. Kato B. Liebenberg G. Hofmann L. Scheepers R.J. Durrheim article Moyer20171333 Article 2017 10.1785/0220160218 Seismological Research Letters 88 1333 – 1338 5 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028305769&doi=10.1785%2f0220160218&partnerID=40&md5=19f0e04ef33a5265b0a229b4219107d1 Cited by: 3 Pamela A. Moyer Margaret S. Boettcher William L. Ellsworth Hiroshi Ogasawara Artur Cichowicz Denver Birch Gerhard Van Aswegen article 2017 10.1126/science.aan6905 Science P. Voosen conference Ogasawara2017237 While mining-induced earthquakes in the deep gold mines of South Africa pose a risk to mines, mineworkers, and the public, they also provide an unusual opportunity to study the physics of earthquakes. The source zone of a M5.5 earthquake that occurred near Orkney, South Africa on 5 August 2014 was well-defined by tens of thousands of aftershocks recorded by instruments deployed as part of a Japanese - South African research project. The upper edge of the M5.5 rupture is located several hundred metres below the mining horizon. A proposal to drill into the M5.5 source zone, as well as several other active faults in other deep mines, was approved by the International Continental scientific Drilling Programme (ICDP) in August 2016. Here we describe the scope and objectives of the project, and the selection and preparation of the principal drilling sites. In addition to the studies of earthquake phenomena, some of the holes will be used by geomicrobiologists to investigate deep microbiological activity fuelled by hydrogen released by seismic rupture to address questions about early life on planet Earth. © 2017 International Society for Rock Mechanics. All Rights Reserved. Conference paper 2017 English 978-192041099-5 ISRM AfriRock - Rock Mechanics for Africa 2017-October International Society for Rock Mechanics 237 – 248 Ritsumeikan University, Kusatsu, Japan; University of the Witwatersrand, Johannesburg, South Africa; Tohoku University, Japan; Institute of Mine Seismology Ltd, South Africa; Council for Geoscience, South Africa; Fukada Geology Institute, Japan; ETH, Switzerland; Seismogen CC, South Africa; Anglogold Ashanti, South Africa; University of New Hampshire, United States; University of Western Australia, Australia; Stanford University, United States; Independent consultant, South Africa; Tel Aviv University, Israel; Princeton University, United States Earth (planet); Earthquakes; Economic geology; Faulting; Gold mines; Rock mechanics; Active fault; African gold mine; Continental scientific drillings; Deep gold mines; Deep-mines; Drilling projects; Microbiological activity; Seismogenic zones; Source zone; South Africa; Infill drilling https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048589628&partnerID=40&md5=d5a56f800a680bc4a854b4dc670d434b Cited by: 7 H. Ogasawara R.J. Durrheim Y. Yabe T. Ito G. Aswegen M. Grobbelaar A. Funato A. Ishida S. Mngadi M.S.D. Manzi M. Ziegler A.K. Ward G. Hofmann P. Moyer M. Boettcher P. Dight W. Ellsworth B. Liebenberg N. Wechsler T. Onstott N. Berset article Yabe20155574 Using a network of sensitive high-frequency acoustic emission sensors, we observed foreshock activity of an Mw 2.2 earthquake (main shock) in a deep gold mine in South Africa. Foreshock activity, which selectively occurred on a part of the rupture plane of the forthcoming main shock, lasted for at least 6 months until the main shock. Rock samples recovered from the main shock source region showed evidence of ancient hydrothermal alteration on the main shock rupture plane, suggesting that the foreshock activity occurred on a preexisting weakness. The foreshocks during 3 months before the main shock were concentrated in three clusters (F1-F3), which we interpret as representing localized preslip at multiple sites. While the location of mining area, the source of stress perturbations, changed with time, the locations of foreshock clusters did not change, suggesting that the preslip patches were controlled by strength heterogeneity rather than stress distribution. Activity over the entire foreshock area was generally constant, but the largest cluster (F2) showed accelerated activity starting at least 7 days before the main shock, while mining stress did not increase in this period. The main shock initiated at a point close to F1, away from F2. All the six foreshocks during the final 41 h occurred in F1 and F2 and in-between. These suggest that in the last stage of the preparation process of the main shock, preslip patches interacted with each other through the stress concentration ahead of the expanding preslip patch (F2), which should be the only driving force of the preparation process under the constant external load. ©2015. American Geophysical Union. All Rights Reserved. 2015 English 21699313 10.1002/2014JB011680 Journal of Geophysical Research: Solid Earth 120 Blackwell Publishing Ltd 5574-5594 Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, Sendai, Japan; Earthquake Research Institute, University of Tokyo, Tokyo, Japan; Department of Civil and Earth Resource Engineering, Graduate School of Engineering, Kyoto University, Kyoto, Japan; GMuG Gesellschaft für Materialprüfung und Geophysik, Bad Nauheim, Germany; GFZ German Research Centre for Geosciences Helmholtz Centre Potsdam, Potsdam, Germany; Now at Japan Atomic Energy Agency, Ibaraki, Japan; College of Science and Engineering, Ritsumeikan University, Kusatsu, Japan; Now at Hitachi Solutions Ltd., Tokyo, Japan 8 acoustic emission; earthquake magnitude; earthquake rupture; fault; foreshock; gold mine; hydrothermal alteration; mining-induced seismicity; nucleation, South Africa https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942552528&doi=10.1002%2f2014JB011680&partnerID=40&md5=dac2840bf08cc545ea9f6de0e2557497 cited By 22 Y. Yabe M. Nakatani M. Naoi J. Philipp T. Watanabe T. Katsura H. Kawakata D. Georg H. Ogasawara