Surface Deformation Related to the 2019 Mw 7.1 and 6.4 Ridgecrest Earthquakes in California from GPS, SAR Interferometry, and SAR Pixel Offsets

Abstract

Abstract We analyzed Synthetic Aperture Radar (SAR) images from Copernicus Sentinel-1A and 1B satellites operated by the European Space Agency and the Advanced Land Observation Satellite-2 (ALOS-2) satellite operated by the Japan Aerospace Exploration Agency and Global Navigation Satellite System (GNSS) data from the Network of the Americas for the 4 July 2019 Mw 6.4 and 5 July (local; 6 July UTC) Mw 7.1 Ridgecrest earthquakes. We integrated geodetic measurements for the 3D vector field of coseismic surface deformation for the two events, using SAR data from Sentinel-1 and ALOS-2 satellites. We combined less precise large-scale displacements from SAR images by pixel offset tracking or matching, including the along-track component, with the more precise SAR interferometry (Interferometric Synthetic Aperture Radar [InSAR]) measurements in the radar line of sight (LoS) direction and intermediate-precision along-track InSAR to estimate all three components of the surface displacement for the two events together. We also estimated the coseismic deformation for the two earthquakes from time-series processing of continuous Global Navigation Satellite System data stations in the area. InSAR coherence and coherence change maps the surface disruptions due to fault ruptures reaching the surface. Large slip in the Mw 6.4 earthquake was on a NE-striking fault that intersects with the NW-striking fault that was the main rupture in the Mw 7.1 earthquake. The main fault bifurcates towards the southeast ending 3 km from the Garlock Fault. The Garlock fault had triggered slip of about 20 mm in the radar LoS along a short section directly south of the main rupture. About 3 km northwest of the Mw 7.1 epicenter, the surface fault separates into two strands that form a pull-apart with about 1 m of down-drop. Further northwest is a wide zone of complex deformation.