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.
- Research Organization:
- University of North Carolina, Chapel Hill, NC; Duke University, Durham, nC
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 889361
- Report Number(s):
- SGP-150-16; TRN: US200619%%802
- Resource Relation:
- Conference: Proceedings, Twentieth Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA, January 24-26, 1995
- Country of Publication:
- United States
- Language:
- English
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