Pre-, Co- and Postseismic GNSS-Corrected Sentinel-1 InSAR Time Series: Moving Beyond the 2019 Ridgecrest, CA Earthquake Sequence

Katherine A. Guns, Xiaohua Xu, David T. Sandwell, & Yehuda Bock

Published August 11, 2021, SCEC Contribution #11268, 2021 SCEC Annual Meeting Poster #099 (PDF)

Interferometric Synthetic Aperture Radar (InSAR) time series methods have become a powerful resource for studying deformation processes occurring on Earth’s surface, particularly in arid environments like those in southern California. One existing challenge that stands in the way of long-term InSAR time series coverage however, is that discontinuities introduced by large-magnitude earthquakes into InSAR time series can cause current atmospheric correction and noise smoothing algorithms to break down. Because sharp offsets violate the assumption of long-term steady deformation, earthquake displacements need to be corrected before applying smoothing and/or atmospheric corrections across the discontinuity. Here, we assess two methods for incorporating the 2019 Ridgecrest, CA, earthquake sequence displacements into a two-year Sentinel-1 InSAR time series for tracks D071 and A064. Descending track results indicate that an SBAS-based method is only able to fully correct the coseismic offset for ~20% of the 62 GNSS station locations included in our scene, and due to noise levels in the time series, only partially corrects or sometimes overcorrects for the rest of our study sites. On the other hand, our Pixel-by-Pixel (PxP) coseismic estimate, calculated using a time series parametric model inversion for each pixel of an InSAR time series grid stack, successfully corrects the coseismic offset for the majority of station comparison sites in our analysis. This PxP analysis also allows us to produce InSAR-derived estimates of deformation during each phase of the earthquake cycle, as well as estimates of seasonal hydrologic processes. To better estimate and explore postseismic motions following the Ridgecrest sequence in our InSAR time series, we apply a GNSS-data based correction to our interferograms. This correction ties the interferograms to GNSS station displacements and removes additional atmospheric artifacts. We present InSAR-based estimates of postseismic deformation for 62 GNSS station locations around the Ridgecrest rupture, as well as a two year coseismic-corrected, GNSS-corrected, atmospheric-corrected InSAR time series dataset. This GNSS-corrected InSAR time series will enable the modeling of postseismic processes such as afterslip in the near field of the rupture, poroelastic deformation at intermediate distances, and viscoelastic deformation at longer time scales in the far field.

Key Words
Sentinel-1 InSAR, GNSS, Ridgecrest, Postseismic

Citation
Guns, K. A., Xu, X., Sandwell, D. T., & Bock, Y. (2021, 08). Pre-, Co- and Postseismic GNSS-Corrected Sentinel-1 InSAR Time Series: Moving Beyond the 2019 Ridgecrest, CA Earthquake Sequence. Poster Presentation at 2021 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy