Dynamic Rupture Simulations of the M6.4 and M7.1 July 2019 Ridgecrest, California Earthquakes

Session: Exploring Rupture Dynamics and Seismic Wave Propagation Along Complex Fault Systems
Type: Oral
Date: 4/29/2020
Time: 03:15 PM
Room: 110 + 140
Description: 

The major events of the 2019 Ridgecrest earthquake sequence were a M6.4 earthquake with primary left-lateral surface rupture that also produced orthogonally oriented aftershocks, followed 34 hours later by a M7.1 earthquake that ruptured through a geometrically complex orthogonal right-lateral fault. The geometry and timing of these earthquakes raises many questions about fault interactions, including: why the first earthquake did not propagate through the right-lateral fault in one larger event, whether the M6.4 earthquake involved any right-lateral structures, whether stress changes from the M6.4 were necessary for the M7.1 to occur, and what was the role of smaller strands of the mapped surface rupture in the overall rupture process.

We use 3D dynamic rupture modeling to address these questions. We find that dynamic clamping and stress shadowing likely confined the M6.4 to the left-lateral fault. We also find that stress changes from the M6.4 were not necessary to allow a M7.1 on the right-lateral fault, but that they affected the slip and likely accelerated the timing of the M7.1. A model geometry that only incorporates the single primary fault plane for each earthquake reproduces the first-order rupture behavior and slip distribution well, but we also consider a model which incorporates more of the secondary mapped fault traces.

Our results have implications not only for the details of the 2019 Ridgecrest earthquakes, but for understanding other earthquake sequences on orthogonal strike-slip faults.

Presenting Author: Julian Lozos

Authors