SCEC Award Number 22041 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Geodetic imaging of earthquakes, fault creep, deformation, and coastal changes at the southern Salton Sea over two decades
Investigator(s)
Name Organization
Junle Jiang University of Oklahoma
Other Participants PhD student Ganiyat Shodunke
SCEC Priorities 1a, 1b, 3f SCEC Groups Geodesy, SDOT, Geology
Report Due Date 03/15/2023 Date Report Submitted 03/15/2024
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, near frequent seismic swarms, earthquakes, and fault creep. In June 2021, a sequence of earthquakes with a maximum magnitude of 5.3 struck the southern shore of the Salton Sea, following a decades-long pattern of active microseismicity occurring in the Brawley Seismic Zone. With previous SCEC support, we have developed a coherence-guided multi-temporal InSAR approach to constrain surface displacement history over the Imperial Valley, including the Salton Sea Geothermal Field (SSGF), from satellite imagery of Envisat (2003–2010) and Sentinel-1A/B satellites (2015–2019). In the SSGF, ground subsidence patterns are highly variable over multiple spatial scales, suggesting that the overlapping effects of regional tectonic and anthropogenic processes play a role. With the 2021 earthquakes being the largest onshore event sequence during the Sentinel-1 operational period, we extend our InSAR time series analysis of the region to the recent two decades. Despite InSAR noise due to agriculture, we derive geodetic deformation maps around June 2021 compared with the seismic sequence. The new observations allow a comparison of the seismic swarm behavior in 2021 and 2005. Furthermore, we design three-dimensional hydromechanical models of heterogeneous geothermal fields with industrial injection or production to produce time-dependent surface deformation signals. These more accurate models help us quantify the biases in source inference if subsurface structural complexity is ignored and improve calculations of stress changes toward unraveling the link between deformation and seismicity.
Intellectual Merit The goal of our project is to use time-dependent, spatially dense geodetic observations to identify, distinguish, and constrain subsurface processes that control the tectonic strain accumulation and release in SSGF and reveal geothermal reservoir conditions subject to energy exploration. This effort helps 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 relation between fluids, deformation, and/or seismicity with improved physical models 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 efforts directly relate to SCEC groups on SDOT and the Community Geodetic Model (CGM). The Community Geodetic Model will be a more reliable and complete product with well-characterized uncertainty and error models. 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 extended InSAR time series for SSGF will complement the larger-scale CGM product and serve as a valuable case study on the resolution and accuracy of the InSAR time series. Our efforts to distinguish geophysical processes using seismo-geodetic observations will help expand the applications of geodetic time series and CGM in SCEC. This project supports an early career researcher (Jiang) and a Ph.D. student coming from communities under-represented in geosciences.
Exemplary Figure Figure 3. Poroelastic deformation at geothermal fields. (a) A three-dimensional finite-element (FE) model for a three-layered structure (thicknesses of h1, h2, and h3). (b) A cross-section view of FE meshes and production well location (star). (c–e) Comparisons of different models illustrate the effect of (c) porosity (homogeneous models), (d) permeability (homogeneous models), and (e) low-permeability/high-porosity caprock (heterogeneous models) on the time evolution of surface deformation. Panel (f) shows near-surface pore pressure evolution for models in (e).