InSAR analysis using both co- and cross-polarized data at Death Valley, California from 2017–2025

The Sentinel-1 satellite mission has been key to the achievement of interferometric synthetic aperture radar (InSAR)-based displacement rates that approach mm/yr precision, particularly in regions without significant vegetation and where long time series of observations exist. However, for more subtle displacement signals, separating the effects of surface processes from deformation due to deeper sources is still challenging. Here, we present a new method based on combinations of co-polarized (VV) and cross-polarized (VH) InSAR data. Cross-polarized data is typically noisier than the co-polarized data and is not widely used for InSAR. However, comparisons of co- and cross-polarized data can allow separation of the contributions from different processes. Signals due to deeper sources, such as slip along faults, should appear the same in both data types, while differences can be due to changes in surface characteristics. We examine VV and VH Sentinel-1 data covering Death Valley, CA, between January 2017 and March 2025. We find that displacement rates derived from VV and VH data differ by several mm/yr in some areas. We also show that rates based only on the VV imagery differ by a few mm/yr between subsets of pixels where the VV-VH differences are large or small, suggesting that VV-VH combinations can help researchers reliably identify pixels that are the least impacted by surface processes. While our work focuses on Death Valley, similar mm/yr-scale biases could impact endorheic basins around the world and influence analyses of interseismic motion, hazard estimates, or groundwater studies.