Stress Changes on the Garlock Fault During and After the 2019 Ridgecrest Earthquake Sequence

Session: Observations From the 2019 Ridgecrest Earthquake Sequence [Poster]
Type: Poster
Date: 4/28/2020
Time: 08:00 AM
Room: Ballroom
Description: 

The recent 2019 Ridgecrest earthquake sequence in Southern California jostled the seismological community by revealing a complex and cascading foreshock series that culminated in a M7.1 mainshock. But the central Garlock fault, despite being located immediately south of this sequence, did not coseismically fail. Instead, the Garlock fault underwent post-seismic creep and exhibited a sizeable earthquake swarm. The dynamic details of the rupture process during the mainshock is largely unknown, as is the amount of stress needed to bring the Garlock fault to failure. We present an integrated view of how fault stresses changed on the Garlock fault during and after the mainshock using a combination of tools including kinematic slip inversion, Coulomb stress change and dynamic rupture modeling. Our results explain several geophysical observations, and we demonstrate from previously developed elastodynamic crack theory that rupture from the mainshock to Garlock fault was dynamically unfavorable. Furthermore, our dynamic model is able to reproduce the main slip asperities during the mainshock and kinematically estimated rupture speeds (~2 km/s) and suggests the change in normal and shear stress on the Garlock fault during the mainshock was greatest near the end of rupture. The largest stress changes on the Garlock fault we observe in our models largely coincide with the creeping region, suggesting that positive stress perturbations could have caused this both during or after the mainshock rupture. This analysis of near-field stress change evolution gives insight into how the Ridgecrest sequence influenced the local stress-field of the northernmost Eastern California Shear Zone.

Presenting Author: Marlon Ramos

Authors