Dynamic rupture simulations of the M6.4 and M7.1 July 2019 Ridgecrest, California earthquakes

Abstract

The largest earthquakes of the 2019 Ridgecrest, California, sequence were a M 6.4 left‐lateral rupture followed 34 hr later by a M 7.1 on a perpendicular right‐lateral fault. We use dynamic rupture modeling to address the questions of why the first earthquake did not propagate through the right‐lateral fault in one larger event, whether stress changes from the M 6.4 were necessary for the M 7.1 to occur, and how the Ridgecrest earthquakes affected the nearby Garlock Fault. We find that dynamic clamping and shear stress reduction confined surface rupture in the M 6.4 to the left‐lateral fault. We also find that stress changes from the M 6.4 were not necessary to allow a M 7.1 on the right‐lateral fault but that they affected the slip and likely accelerated the timing of the M 7.1. Lastly, we find that the Ridgecrest earthquakes may have brought the central Garlock Fault closer to failure.