GNSS and InSAR integration for 3-D crustal deformation in California and western Nevada

Zheng-Kang Shen, & Zhen Liu

Submitted November 14, 2024, SCEC Contribution #14121

The regions of California and Nevada are shaped by dynamic tectonic and hydrologic processes that contribute to significant crustal deformation. Tectonic activities, such as fault slip along major fault systems, interact with hydrologic processes such as groundwater circulation, leading to complex surface deformation. Monitoring and understanding these deformation phenomena are essential for assessing seismic hazards, managing groundwater resources, and mitigating risks to infrastructure and communities. In this study we develop a method to integrate Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR) observations to investigate crustal deformation associated with both tectonic and hydrologic activities. This method adopts an optimal approach to interpolate discrete GNSS velocity data points into a continuous velocity field, takes a pragmatic approach to evaluate uncertainties in both InSAR and GNSS measurements for data weighting, optimally estimates and removes orbital errors in InSAR data, and synthesizes InSAR Line of Sight (LOS) measurements with interpolated GNSS data to solve for 3-D deformation through least-squares regression.

We apply the method to integrate GNSS and InSAR data to probe crustal deformation across California and western Nevada. Up to three decades of GNSS data are incorporated, and combined with InSAR data acquired using various satellites and sensors covering similar time periods. Our 3-D deformation results reveal the following: (1) In the plate boundary zone of California and western Nevada, tectonic deformation is dominated by faulting around the San Andreas and Walker Lane fault systems, with dextral shear motion of ~30-40 mm/yr and ~8-12 mm/yr, respectively. While most of the deformation can be attributed to slip beneath known tectonic faults, significant residual deformation remains and is broadly distributed, particularly across the Walker Lane fault system. (2) Significant subsidence is observed in the San Joaquin and Sacramento Valleys, at rates of 150-250 mm/yr and 10-25 mm/yr, respectively. Notable subsidence of 6-10 mm/yr is seen along the California coastline, while the Santa Maria Basin and Oxnard Plain experience subsidence of up to 15 mm/yr. Uplifts of 3-8 mm/yr are detected in the mountains surrounding the San Joaquin Valley. (3) Abrupt vertical offsets are observed across various tectonically active faults, caused by differential subsurface mass movement. It suggests that faults, acting as hydraulic barriers, can modulate vertical deformation driven by groundwater circulation, associated with dynamic groundwater recharge and extraction within the underlying aquafer system.

Citation
Shen, Z., & Liu, Z. (2024). GNSS and InSAR integration for 3-D crustal deformation in California and western Nevada. J. Geophys. Res.-Solid Earth, (submitted).

Related Projects & Working Groups
Tectonic Geodesy