Project Abstract
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We have analyzed geodetic deformation and seismicity prior and after the 2019 Ridgecrest earthquake sequence. We were able to extract the postseismic signal from other sources of deformation using an Independent Component Analysis. We were expecting to see a possibly prominent signal associated with the Coso area where the geothermal gradient is steep. Instead we were able to extract a clear regional signal at the scale of Southern California a whole. We haven’t completed the analysis and modeling of this signal yet. The project has focused on analyzing the cause for the lack of aftershocks and geodetic deformation in the area of the Coso geothermal field. The seismicity and surface deformation observations show that the geothermal operation induced surface subsidence and a burst of seismic activity that decayed gradually over 10-20 years. We were able to demonstrate, based on thermo-hydromechanical modeling, that this evolution resulted mostly from thermal contraction and was in fact mostly aseismic. It resulted in a shear stress reduction that explains the lack of aftershocks around Coso in 2019. |
