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

The regions of California and Nevada are shaped by dynamic tectonic and hydrologic processes that drive significant crustal deformation. In this study we use the method of [Shen and Liu, 2020] to integrate Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR) observations to investigate deformation from both tectonic and hydrologic activities. This method includes interpolating GNSS velocity data into a continuous velocity field, evaluating uncertainties in GNSS and InSAR measurements, correcting orbital errors in InSAR data, and combining InSAR Line-of-Sight measurements with GNSS data to resolve 3-D deformation using least-squares regression. We apply this method to three decades of GNSS and InSAR data across California and western Nevada. Key findings include: (1) Faulting along the San Andreas and Walker Lane fault systems drives dextral shear motions of 30–40 mm/yr and 8–12 mm/yr, respectively. Residual deformation, however, is broadly distributed within the fault systems, particularly in the Walker Lane region, suggesting contributions from ductile flow in the lower crust. (2) Significant subsidence, caused by drought and excessive groundwater withdrawal, is observed in the San Joaquin and Sacramento Valleys, at rates of 150-250 mm/yr and 10-25 mm/yr, respectively. Uplift rebound of 3-8 mm/yr is observed in the mountains surrounding the San Joaquin Valley. Notable subsidence of 6-12 mm/yr is also seen along the California coastline, while the Santa Maria Basin and Oxnard Plain experience subsidence of up to 15 mm/yr. (3) Abrupt vertical offsets are observed across various tectonically active faults, suggesting fault-modulated hydrological deformation.