Modeling the 2019 Ridgecrest Earthquake Sequence

The July 2019 Ridgecrest earthquake sequence ruptured two nearly-perpendicular conjugate fault planes within 36 hours of each other. It also produced a rich set of aftershocks outlining the ruptured fault surfaces, but also triggered events in the Coso Geothermal Field and along the Garlock fault. Of particular scientific interest are the short-term (coseismic) and longer-term stress interactions between the foreshock, different parts of the mainshock, and aftershocks; these interactions may provide a physical mechanism and possible structural control over this remarkable series of events. Toward this goal, we model the dynamics of the M6.4 and M7.1 events using the 3D finite element method (Barall, 2009), incorporating up-to-date estimates of the fault geometry. We experiment with different stress parameterizations, including regional stress field estimates, as well as estimates of the stress transfer caused by the major faulting events. We also attempt to fit inferred slip patterns from geodetic models and other data. Our aim is to understand the dynamics of this unique series of earthquakes, with implications for seismic hazard in Southern California and beyond.