Complex Rupture of an Immature Fault Zone: A Simultaneous Kinematic Model of the 2019 Ridgecrest, CA Earthquakes

The July 4, 2019 Mw6.4 and subsequent July 6, 2019 Mw7.1 Ridgecrest Sequence earthquakes ruptured orthogonal fault planes in the Little Lake Fault Zone, a low slip rate (1 mm/yr) dextral fault zone in the area linking the Eastern California Shear Zone and Walker Lane. This region accommodates nearly one fourth of plate boundary motion and has been proposed to be an incipient transform fault system that could eventually become the main tectonic boundary, replacing the San Andreas. We investigate the rupture process of these events using a novel simultaneous kinematic slip method with joint inversion of high-rate GNSS, strong motion, GNSS static offset, and InSAR data. We model the Coulomb stress change to evaluate how the first mainshock may have affected the second. Our findings suggest complex interactions between several fault structures, including dynamic and static triggering, and provide important context for regional seismic source characterization and hazard models.