Characterization of geothermal reservoir crack patterns using shear‐wave splitting

Microearthquakes recorded by a downhole, three‐component seismic network deployed around the Coso, California, geothermal reservoir since 1992 display distinctive shear‐wave splitting and clear polarization directions. From the polarizations we estimated three predominant subsurface fracture directions, and from the time delays of the split waves we determined tomographically the 3-D fracture density distribution in the reservoir.