GNSS and InSAR Integration for 3-D Deformation Field in Southwestern US

Zheng-Kang Shen, & Zhen Liu

Submitted September 11, 2022, SCEC Contribution #12429, 2022 SCEC Annual Meeting Poster #078

We have developed a 3-dimensional (3-D) GNSS and InSAR integration algorithm, in which discrete GNSS data points are first interpolated to obtain a 3-D continuous velocity field and then combined with the InSAR line-of-sight (LOS) velocity data pixel by pixel using a least-squares method. This approach has the advantages of a) optimally interpolating the GNSS data, b) using realistically estimated uncertainties for the interpolated GNSS velocities and InSAR LOS rates to weight the data for solution, and c) globally estimating ramps and/or offsets for all input InSAR images to minimize the data misfit.

We apply the method to a compilation of GNSS and InSAR data in southwestern US for its 3-D velocity field. We use velocity solutions of continuous GNSS sites produced by the NASA-Scripps MEaSUREs project ( and the SAR data of multiple satellites (ERS-1,2, Envisat, Sentinel-1, ALOS-2 ScanSAR) which jointly cover the time span of 1992 to 2021.

Application of our integration method to GNSS and InSAR data shows its capability of successfully restoring 3-D continuous deformation field from spatially limited GNSS and dimensionally limited InSAR data. The GNSS and InSAR data are generally consistent for the horizontal velocities at sub-millimeter per year level. The vertical velocity field is determined much better than using GNSS data only, especially for regions experiencing localized tectonic/hydrological/anthropogenic deformation. Our preliminary results show that the regions such as the Santa Maria Basin, Oxnard Plain, Brawley Seismic Zone, and Imperial Valley experience the hydrologic and geothermal processes induced subsidence of ~3-8 mm/yr. The San Francisco Bay area between the San Andreas-Sargent and Hayward fault is found uplifting at a rate up to 5 mm/yr, and the spatially bounded uplift pattern by the two faults suggests fault controlled vertical deformation. Large subsidence of up to 100-200 mm/yr is also observed in portions of the Central Valley, and an uplift of about 5 to 10 mm/yr is detected in the Southern Coastal Ranges between the Kettleman Hills-Lost Hills thrust and the San Andreas fault, possibly related to the droughts and groundwater withdrawal in the Central Valley. The highest uplift (~12 mm/yr) is found along the west margin of the Central Valley located east of the thrust. Subsidence of a few mm/yr is also seen in parts of the northwest and southwest Nevada.

Key Words
GNSS, InSAR, velocity, combination, Southwestern US

Shen, Z., & Liu, Z. (2022, 09). GNSS and InSAR Integration for 3-D Deformation Field in Southwestern US. Poster Presentation at 2022 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy