A Statewide InSAR Velocity Map for California Produced by a Comprehensive Large Scale Analysis of ARIA Standard Products

Abstract

Routine Synthetic Aperture Radar (SAR) acquisitions from the Sentinel‐1 constellation enable monitoring of slow surface deformation (millimeters to centimeters per year), yet consistent and accessible pathways for producing validated, user‐ready velocity products remain limited. Here we present (a) a statewide Interferometric SAR (InSAR) line‐of‐sight secular surface velocity map for California derived from standardized Advanced Rapid Imaging and Analysis Sentinel‐1 Geocoded Unwrapped Phase (ARIA‐S1‐GUNW) products spanning 2014–2023, and (b) the details of a scalable processing and validation workflow for producing similar maps. Our workflow leverages several open‐source software tools for post‐processing of GUNW products, time series analysis, corrections for noise, and removal of earthquakes and transient signals. We apply it to data from nine ascending and descending Sentinel‐1 tracks across California, and validate the output against Global Navigation Satellite Systems (GNSS) data. The resulting velocity fields resolve tectonic and anthropogenic deformation signals, including elastic strain accumulation and shallow creep along the San Andreas Fault system, rapid subsidence exceeding 10 cm/yr in the Central Valley, and localized deformation associated with groundwater withdrawal and landsliding. We find millimeter‐per‐year agreement with GNSS velocities, and estimate typical velocity uncertainties to be ≤1 mm/yr over coherent terrain, increasing locally in regions of strong deformation gradients and/or decorrelation. Our velocity map provides an accessible data set for non‐specialists to investigate multiple sources of slow secular deformation across California; our workflow can also be used with GUNW products from the NASA‐ISRO SAR (NISAR) mission, enabling the leveraging of that rich data source in the future.