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Title: Locating an active fault zone in Coso geothermal field by analyzing seismic guided waves from microearthquake data

Active fault systems usually provide high-permeability channels for hydrothermal outflow in geothermal fields. Locating such fault systems is of a vital importance to plan geothermal production and injection drilling, since an active fault zone often acts as a fracture-extensive low-velocity wave guide to seismic waves. We have located an active fault zone in the Coso geothermal field, California, by identifying and analyzing a fault-zone trapped Rayleigh-type guided wave from microearthquake data. The wavelet transform is employed to characterize guided-wave's velocity-frequency dispersion, and numerical methods are used to simulate the guided-wave propagation. The modeling calculation suggests that the fault zone is {approx} 200m wide, and has a P wave velocity of 4.80 km/s and a S wave velocity of 3.00 km/s, which is sandwiched between two half spaces with relatively higher velocities (P wave velocity 5.60 km/s, and S wave velocity 3.20 km/s). zones having vertical or nearly vertical dipping fault planes.
Authors:
Publication Date:
OSTI Identifier:
889361
Report Number(s):
SGP-150-16
TRN: US200619%%802
Resource Type:
Conference
Resource Relation:
Conference: Proceedings, Twentieth Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA, January 24-26, 1995
Research Org:
University of North Carolina, Chapel Hill, NC; Duke University, Durham, nC
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; 15 GEOTHERMAL ENERGY; CALIFORNIA; DRILLING; GEOTHERMAL FIELDS; MICROEARTHQUAKES; P WAVES; PRODUCTION; RESERVOIR ENGINEERING; S WAVES; SEISMIC WAVES; SIMULATION; VELOCITY; Geothermal Legacy