HR: 16:00h
AN: S52I-01    [PDF]
TI: Four-dimensional tomography reveals changes in structure 1996 - 2002 at the Coso geothermal area, California
AU: * Julian, B R
EM: julian@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., MS 977, Menlo Park, CA 94025 United States
AU: Foulger, G R
EM: g.r.foulger@durham.ac.uk
AF: University of Durham, Science Laboratories, South Rd., Durham, DH1 3LE United Kingdom
AU: Monastero, F C
EM: francis.monastero@navy.mil
AF: Geothermal Program Office, NAWS, Code 837000D, 1 Administration Circle, China Lake, CA 93555 United States
AU: Richards-Dinger, K
EM: keith.richards-dinge@navy.mil
AF: Geothermal Program Office, NAWS, Code 837000D, 1 Administration Circle, China Lake, CA 93555 United States
AB: The Coso geothermal area, at the southern end of Owens Valley in eastern California, has been commercially exploited for electricity generation for more than a decade. Seismic activity in the area is monitored by a network of three-component digital borehole seismometers operated by the US Navy, and several thousand locatable earthquakes occur each year. This situation is ideal for Local Earthquake Tomography. Inversions for three-dimensional Vp and Vp/Vs structure with resolution of 2 km horizontally and 1 km vertically show that between 1996 and 2002 the Vp/Vs ratio decreased at depths shallower than 2 km below the surface, primarily because of an increase in Vs. This change might be caused by either drying of the rock matrix or decrease in the pore pressure. Time-varying tomography of this kind, previously applied to Long Valley caldera and The Geysers geothermal field, provides a method of monitoring physical changes such as fluid depletion in volcanoes and exploited geothermal reservoirs.
DE: 7205 Continental crust (1242)
DE: 7230 Seismicity and seismotectonics
DE: 7294 Instruments and techniques
DE: 8424 Hydrothermal systems (8135)
DE: 8494 Instruments and techniques
SC: Seismology [S]
MN: 2003 Fall Meeting