Using Micro-Seismicity and Seismic Velocities to Map Subsurface Geologic and Hydrologic Structure Within the Coso Geothermal Field California

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Conference Paper: Using Micro-Seismicity and Seismic Velocities to Map Subsurface Geologic and Hydrologic Structure Within the Coso Geothermal Field California

Abstract

We relocate 14 years of seismicity in the Coso Geothermal Field using differential travel times and simultaneously invert for seismic velocities to improve our knowledge of the subsurface geologic and hydrologic structure. We utilize over 60,000 micro-seismic events using waveform crosscorrelation to augment the expansive catalog of Pand S-wave differential arrival times recorded at Coso. We further carry out rigorous uncertainty estimation and find that our results are precise to within 10s of meters of relative location error. Relocated micro-seismicity outlines major, throughgoing faults in the reservoir in some cases, although a significant portion of seismicity remains diffuse and does not cluster into sharply defined structures. The seismic velocity structure reveals heterogeneous distributions of compressional (Vp) and shear (Vs) wave speed, with Vp generally lower in the main field when compared to the east flank and Vs varying more significantly in the shallow portions of the reservoir. The Vp/Vs ratio appears to outline the two main compartments of the reservoir at depths of approximately 0.5 to 2 km, with a ridge of relatively high Vp/Vs separating the main field from the east flank. In the deeper portion of the reservoir this ridge is less prominent. Our results indicate that highprecision relocations of micro-seismicity and associated velocity inversions can provide useful insights into subsurface structural features and hydrologic compartment boundaries within the Coso

Geothermal Field.

Authors 
J. O. Kaven, S. H. Hickman and N. C. Davatzes






Conference 
Stanford Geothermal Conference; Stanford, California; 2012/01/30


Published 
Stanford University, 2012





DOI 
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Online 
Internet link for Using Micro-Seismicity and Seismic Velocities to Map Subsurface Geologic and Hydrologic Structure Within the Coso Geothermal Field California

Citation

J. O. Kaven,S. H. Hickman,N. C. Davatzes. 2012. Using Micro-Seismicity and Seismic Velocities to Map Subsurface Geologic and Hydrologic Structure Within the Coso Geothermal Field California. In: PROCEEDINGS, Thirty-Seventh Workshop on Geothermal Reservoir Engineering Stanford University. Stanford Geothermal Conference; 2012/01/30; Stanford, California. Stanford, California: Stanford University; p. 8