Seismic velocity structure and microearthquake source properties at The Geysers, California, geothermal area

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1986

OSTI ID:5859325

O'Connell, D R

The method of progressive hypocenter-velocity inversion has been extended to incorporate S-wave arrival time data and to estimate S-wave velocities in addition to P-wave velocities. Results of a P and S-wave progressive hypocenter-velocity inversion at The Geysers show that the top of the steam reservoir is clearly defined by a large decrease of V/sub p/ + V/sub s/ at the condensation zone-production zone contact. The depth interval of maximum steam production coincides with minimum observed V/sub p/ + V/sub s/, and V/sub p/ + V/sub s/ increases below the shallow primary production zone suggesting that reservoir rock becomes more fluid saturated. The moment tensor inversion method was applied to three microearthquakes at The Geysers. Estimated principal stress orientations were comparable to those estimated using P-wave first motions as constraints. Well constrained principal stress orientations were obtained for one event for which the 17 P-first motions could not distinguish between normal-slip and strike-slip mechanisms. The moment tensor estimates of principal stress orientations were obtained using far fewer stations than required for first-motion focal mechanism solutions. The three focal mechanisms obtained here support the hypothesis that focal mechanisms are a function of depth at The Geysers. Progressive inversion as developed here and the moment tensor inversion method provide a complete approach for determining earthquake locations, P and S-wave velocity structure, and earthquake source mechanisms.

• Research Organization: California Univ., Berkeley (USA)
• OSTI ID: 5859325
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150201* -- Geology & Hydrology of Geothermal Systems-- USA-- (-1989)
58 GEOSCIENCES
580201 -- Geophysics-- Seismology & Tectonics-- (1980-1989)
CALIFORNIA
DATA ANALYSIS
DEPTH
DIMENSIONS
EARTHQUAKES
FEDERAL REGION IX
GEOPHYSICAL SURVEYS
GEOTHERMAL FIELDS
GEYSERS GEOTHERMAL FIELD
HYPOCENTERS
MEASURING METHODS
MICROEARTHQUAKES
NORTH AMERICA
RESERVOIR ROCK
SATURATION
SEISMIC EVENTS
SEISMIC P WAVES
SEISMIC S WAVES
SEISMIC SOURCES
SEISMIC SURVEYS
SEISMIC WAVES
STEAM
STRESS ANALYSIS
SURVEYS
USA
VELOCITY
WATER SATURATION
WAVE PROPAGATION