SCEC Award Number 19076 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Forecasting induced seismicity
Investigator(s)
Name Organization
Jean-Philippe Avouac California Institute of Technology
Other Participants Dr. Kyungjae Im, Post Doc
TBD, Grad Student
SCEC Priorities 5e, 3f, 1e SCEC Groups FARM, EFP, Seismology
Report Due Date 03/15/2020 Date Report Submitted 02/27/2020
Project Abstract
 We investigated the relationship between effective stress variations and seismicity induced by fluid injection or extraction for geothermal energy production. We focused on two case examples of geothermal plants in California at Brawley (Imperial valley) and Coso (Owens Valley). Based on thermo-mechanical modelling and the analysis of seismicity and surface deformation we find that in both cases thermal effects play a major role in driving deformation, aseismic fault slip and seismicity. A major finding is that thermal stresses seem to explain the gap of aftershocks at Coso following the Ridgecrest earthquake.
Intellectual Merit The study demonstrates that thermal stresses play an important role in driving seismicity in case of geothermal operations. Thermal stresses can be be quantitatively taken into account in addition to poroelastic stresses to assess temporal and spatial variations of seismicity.
Broader Impacts The research provides new insight on an overlooked factor of seismic hazard associated to to geothermal energy production. The research is also relevant to assess the mechanical integrity of CO2 storage and potential seismic hazard as thermal effects are also likely to be significant.
Exemplary Figure Figure 4. A: Seismicity before and after the 2019 Mw 7.1 Ridgecrest mainshock. Blue circles denote 20 days of aftershocks (M>2; USGS, earthquake.usgs.gov), yellow star denotes epicenter of M7.1 earthquake, black line denotes fault geometry of Ridgecrest earthquakes, gray circles denote relocated seismicity during 1981 – 2017 (M>1). Note the gap of aftershocks around Coso despite the high seismicity prior to 2019. Inset: zoomed-in view of the Coso geothermal field.. B: Static Coulomb stress change for right-lateral fault parallel to the main right-lateral fault (red fault in Fig.1 inset) due to the Mw 7.1 2019 events assuming a coefficient of friction 0.6. Dots denote Ridgecrest aftershocks (M>2). C: Depth distribution of earthquakes of section XX’ in panel A (all events in orange box) with co-seismic slip distribution (red area). D: Coulomb stress rate at the center of the reservoir due to thermal contraction and brittle failure of the reservoir compared with seismicity rate around Coso.