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

Zheng-Kang Shen, & Zhen Liu

Published September 8, 2024, SCEC Contribution #13885, 2024 SCEC Annual Meeting Poster #080

We develop a method to integrate observations of Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR) for the investigation of crustal deformation associated with tectonic and hydrologic activities. This method has the following ingredients: It adopts an optimal approach to interpolate discrete GNSS velocity data points into a continuous velocity field; it takes a pragmatic approach to evaluate uncertainties for InSAR and GNSS measurements and the interpolated GNSS velocities, to be used as weights for data input; the ramp parameters of multiple tracks of InSAR data are solved through global optimization to minimize systematic biases in the solution; and InSAR LOS data are averaged within small grids, and de-ramped InSAR data and interpolated GNSS data are aggregated to solve for 3-D deformation through least-squares regression.

We apply the method to integrate GNSS and InSAR data to probe 3-D crustal deformation of California and western Nevada. Up to 3 decades of GNSS data are incorporated, observed in both continuous and campaign modes, and combined with InSAR data acquired using various satellites and sensors spanning over similar time periods. Our 3-D deformation results show the following: (1) Horizontal crustal deformation at the plate boundary zone in California and western Nevada is dominated by tectonic deformation around the San Andreas fault and Walker Lane fault systems, with ~30-40 mm/yr and ~10-15 mm/yr sinistral shear motion across them, respectively. Most of the deformation field can be interpreted as slip underneath known tectonic faults in the region, but the residual deformation field is still significant and broadly distributed, particularly across the Walker Lane fault system. (2) Subsidence is widely spread in the San Joaquin Valley and Sacramento Valley, with the rates reaching 150-250 mm/yr and 10-25 mm/yr in the two valleys, respectively. Significant subsidence of 6-10 mm/yr is seen along the California coastline, and up to 15 mm/yr subsidence is found in the Santa Maria Basin and Oxnard Plain. Uplifts of 3-8 mm/yr are detected in the mountains surrounding the San Joaquin Valley. (3) Abrupt vertical offsets are revealed across a wide range of tectonically active faults, suggesting that faults as hydraulic barriers, can modulate vertical deformation driven by groundwater circulation, associated with dynamic supplement and extraction of groundwater in the substrate aquafer system.

Key Words
GNSS, InSAR, integration, deformation, California

Citation
Shen, Z., & Liu, Z. (2024, 09). GNSS and InSAR integration for 3-D crustal deformation of California and western Nevada. Poster Presentation at 2024 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy