Long Valley Exploratory Well

Description

A scientific drilling effort has been proposed to deepen an existing 2-km deep hole to a target depth of between 3.5 and 4.0 km. The borehole is located near the center of the resurgent dome of Long Valley Caldera in east-central California. Deepening the well has been accomplished by continuous H-size coring (2.5" diameter core) to the target depth. The ICDP with 80% matching funds from the California Energy Commission (CEC), the U.S. Department of Energy (DoE), and the U.S. Geological Survey (USGS) supported the project. Long Valley Caldera has shown sustained unrest since 1980 characterized by recurring earthquake swarms, inflation (dome-shaped uplift) of the resurgent dome, and increased levels of fumarolic activity accompanied by high concentrations of carbon dioxide (CO₂) gas in the soils around Mammoth Mountain on the southwest margin of the caldera. The existing 2-km-deep hole is located directly over the center of inflation in the resurgent dome (total uplift since 1979 is 60 cm and the current uplift rate is 2-3 cm/y) and at the northern margin of the earthquake swarm activity.
Scientific goals of the proposed drilling were to shed light on the nature of processes at mid-crustal depths in areas of active deformation by drilling into the seismogenic volume beneath the resurgent dome and
- obtaining a complete core section for studies of the petrology, fracture state, and pore fluids,
- determining the temperature profile below the hydrologic convective regime that appears to control temperature shallower than 2 km,
- determining the state of stress within the seismogenic volume, and
- modeling present-day hydrothermal conditions.
In the long term, the hole is being used as a geophysical observatory with a number of down-hole instrument packages to track processes occurring directly above the inflating magma chamber driving unrest in the caldera.

(Photo ©:ICDP)

See also:

ICDP-13/97

Location

North America, United States of America, California, Sierra Nevada, Long Valley Caldera

Coordinates

37° 40' 47'' N, 118° 54' 31'' W (Please scroll down to end of page for more information.)

Project Start and End

Begin of drilling June 15, 1998
End of drilling September 15, 1998

Programs and Funding

Principal Investigators

David P. Hill, U.S. Geological Survey, USGS, Sacramento
John Sass, U.S. Geological Survey, USGS, Flagstaff
John Traver Finger, Sandia National Laboratories

Cooperating Principal Investigators

Roy A. Bailey, U.S. Geological Survey, USGS, Sacramento
Christoph Clauser, Geophysica Beratungsgesellschaft mbH
Christoph Clauser, RWTH Aachen University, Applied Geophysics
John C. Eichelberger, U.S. Geological Survey, Volcano Hazards Program
William L. Ellsworth, U.S. Geological Survey, USGS, Menlo Park, Earthquake Hazards Program - Northern California
Christopher D. Farrar, U.S. Geological Survey, USGS, Sacramento
Stephen H. Hickman, U.S. Geological Survey, USGS, Menlo Park, Earthquake Hazards Program - Northern California
Paul Kasameyer, Lawrence Livermore National Laboratory, Earth Science Division
Vicki Sue McConnell, Oregon Department of Geology and Mineral Industries
Michael L. Sorey, U.S. Geological Survey, USGS, Sacramento
John W. Valley, University of Wisconsin at Madison, Department of Geology and Geophysics
Daniel F.C. Yang, Shell Canada Ltd., Unconventional Heavy Oil Recovery
Mark D. Zoback, Stanford University, Department of Geophysics

Partners and Contractors

Keywords

Caldera , California , Drilling , ICDP-13/97 , Long Valley , LVEW , Thermal Regimes , U.S.A. , Volcanic Systems

Current State

Drilling operations and scientific evaluations have been finalized, downhole monitoring is ongoing

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