Surface Displacement and Source Model Separation of the Two Strongest Earthquakes During the 2019 Ridgecrest Sequence: Insights From InSAR, GPS, and Optical Data

Abstract

AbstractSince the occurrence of the 2019 Mw 6.4 and Mw 7.1 Ridgecrest earthquake sequence in the Eastern California Shear Zone, coseismic deformation following the two earthquakes has been intensively studied, and source modeling with interferometric synthetic aperture radar (InSAR), Global Positioning System (GPS) and seismological datasets has been favored. However, we recently found that the coseismic modeling of the two earthquakes constrained by the dense near‐field Planet‐Lab optical measurements can be more detailed than the previously estimated, which requires an accurate Planet‐Lab displacement. In this study, we improve the long wavelength orbital ramps correction method for obtaining a more accurate Planet‐Lab horizontal displacement field. The corrected dense near‐field Planet‐Lab data are firstly used together with the intermediate‐field GPS data to invert and distinguish the fault slip distribution for the two earthquakes. The same scheme is used to simultaneously invert the InSAR, SAR, GPS, and optical datasets, to improve the constraints on seismic source parameters. Our inversion results show that the joint‐event slip model is rougher than the two single‐event slip models, but it has a more concentrated slip pattern and larger slip amplitude in some zones. We show that adding a near‐field constraint of the Planet‐Lab data in the combined‐data inversion can reduce the slip parameter uncertainty and enhance the model resolution. The Coulomb failure stress changes on the southeastern Blackwater, the southern Owens Valley, and the central Panamint Valley faults are enhanced by about 0.4–0.8 bar by the 2019 Ridgecrest earthquake sequence.