SCEC Award Number 20139 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Distinguishing between Tectonic and Anthropogenic Processes in the Salton Sea Geothermal Field
Name Organization
Rowena Lohman Cornell University Junle Jiang Cornell University
Other Participants Kyle Murray (graduate student, funded through other agencies, but travel funds requested here).
SCEC Priorities 1a, 1b, 3f SCEC Groups Geodesy, Geology, Seismology
Report Due Date 03/15/2021 Date Report Submitted 05/10/2021
Project Abstract
The Imperial Valley in Southern California is a tectonically active region, where widespread agricultural activity and geothermal energy exploration have been ongoing for decades, in proximity to frequent seismic swarms, earthquakes and fault creep. In this project, we seek to advance the understanding of faulting and fluid injection and production using high-resolution surface displacement at the Salton Sea Geothermal Field (SSGF) constrained by multi-temporal InSAR deformation data. We propose to explore the spatial and temporal relation between these deformation sources and seismicity, through the use of end-member models of subsurface processes. The Sentinel-1a/b satellites, which have been operating since 2014, allows us to characterize the surface displacement in this region with better temporal sampling and data quality over a 5-year period. In the SSGF, ground subsidence patterns are highly variable over a range of spatial scales, suggesting that the overlapping effects of regional tectonic and anthropogenic processes play a role. We test models of tectonic faulting and subsurface volumetric sources representing fluid injection and production, and compare with earlier periods (Envisat, 2003–2010) in which transient fault creep and ground uplift/subsidence were documented. Furthermore, we compare strain and stress changes associated with our inferred sources with seismicity catalogs, with the goal of understanding the potential link between long-term deformation and seismicity.
Intellectual Merit The goal of our project is to use spatially dense time-dependent observation from recent satellite missions to investigate and differentiate processes that control the strain accumulation in SSGF, the transitional regime between the San Andreas and Imperial faults. This effort would help address research priorities in SCEC5 such as P1.a. “Refine the geologic slip rates on faults in Southern California ... optimally combine the geologic data with geodetic measurements to constrain fault-based deformation models, accounting for observational and modeling uncertainties.” Exploring the connection between subsurface source models and seismicity will contribute to P3.f. ” Study the mechanical and chemical effects of fluid flows, both natural and anthropogenic, on faulting and earthquake occurrence...”
Broader Impacts Our effects are directly relevant to SCEC groups on SDOT and the Community Geodetic Model (CGM). The Community Geodetic Model will be a more reliable and complete product if we can include estimates of the confidence that we can place on the modeled variations in displacement rates across a range of scales. This project focuses on an important tectonic region within SCEC’s area of interest, the Salton Trough, which has been challenging for geodetic studies due to land surface and vegetation changes and agricultural activities. Our detailed InSAR analysis for SSGF will complement the larger-scale CGM product and serve as a valuable case study on the resolution and accuracy of InSAR time series. Our efforts to distinguish different geophysical processes using InSAR data and potentially bridge between geodetic and seismic phenomena would help expand the applications of geodetic time series and CGM in SCEC.
Exemplary Figure Figure 3. InSAR observations and anthropogenic deformation due to geothermal operation at the SSGF. (a) Filtered LOS surface velocity field in SSGF (with a spatially uniform shift of 10 mm/yr compared to Figure 2). (b) LOS surface displacements due to fluid injection and production at SSGF. Injection and production wells are shown as red and brown triangles, respectively. (c) The total injected and produced fluid mass at individual wells of the SSGF over 2015–2019.