SCEC Award Number 20141 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Rheological implications of post-seismic deformation following the 2019 Ridgecrest Earthquakes
Investigator(s)
Name Organization
Jean-Philippe Avouac California Institute of Technology
Other Participants Dr. Camilla Penney, Post Doc
SCEC Priorities 5e, 3e, 3b SCEC Groups Geodesy, SDOT, FARM
Report Due Date 03/15/2021 Date Report Submitted 05/07/2021
Project Abstract
 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.
Intellectual Merit The study provides fundamental insight:
- on the effect of fluid injection on seismicity.
- on the rheological properties of the lithosphere
Broader Impacts Several students and postdocs were trained as par tof this study.
The findings will probably arise interest from the media and broader audience.
Exemplary Figure The proposed exemplary figure (see technical report) illustrates the key finding of the study: thermal distressing has suppressed aftershocks in the area of the Coso Geothermal Field (figure produced by Kyungjae (KJ) Im and JP Avouac).