SCEC Award Number 20147 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Earthquake Gates: Investigating the Role of Seismic Waves in Multi-fault Rupturing
Investigator(s)
Name Organization
Hector Gonzalez-Huizar University of Texas at El Paso Roby Douilly University of California, Riverside
Other Participants
SCEC Priorities 1e, 1d, 4a SCEC Groups Seismology, SAFS, FARM
Report Due Date 03/15/2021 Date Report Submitted 03/15/2024
Project Abstract
 This project seeks to assess the effect of dynamic triggering of multi-fault rupture with application to the Cajon Pass area. Dynamic triggering on a fault occurs when the passing of seismic waves alters the mechanical state or properties of the fault, weakening it and advancing its failure. Recent studies have shown that in some cases of multi-fault ruptures the seismic waves generated by the failure in one of the faults plays an important role in triggering the failure of the subsequent faults. Here we present our results of a project that aims to evaluate the role of seismic wave-related stress in promoting multi-fault ruptures, specifically, in a potential propagation of a rupture on the San Jacinto Fault (SJF) onto the San Andreas Fault (SAF). This project combines dynamic rupture modeling with dynamic stress modeling (the related to seismic waves) to assess a potential multi-fault rupture scenery across the Cajon Pass area. The fault geometry is derived from the SCEC Community Fault Model and we consider 2 configurations for the SJF where in configuration A, the SJF adopts the Middle San Jacinto (MSJ) strand but in configuration B, it takes the Glen Helen (GH) strand which is closer to the SAF. Using a regional stress regime with different stress orientations, our results show that even when the rupture is not able to propagate from the SJF to the SAF, a temporary dynamic stress increase, caused by the passing seismic waves, can be observed on sites along the SAF fault.
Intellectual Merit This project combines dynamic rupture modeling with dynamic stress modeling to assess the effect of dynamic triggering of multi-fault rupture with application to the Cajon Pass area in particular near the junction of the San Andreas fault with the San Jacinto fault. The seismic waves for a rupture initiated on the SJF can damage segments of the SAF ahead of the rupture front which could facilitate the propagation of the SJF rupture onto the SAF. Using dynamic rupture simulation with different characteristics (such as geometry, stress conditions) will permit to have a more realistic scenario to investigate the potential weakening that seismic waves from a rupture on the SJF can cause along the SAF, and its role in facilitating a throughgoing rupture between those segments.
Broader Impacts This proposed work has broader impacts on the assessment of seismic hazard in Cajon Pass region. Understanding how dynamic stress triggering can facilitate rupture between the San Jacinto and San Andreas is vital to understand the ability of the Southern San Andreas fault to generate cascade events that will lead to large earthquakes in this region.
Exemplary Figure Figure 3.

Slip distribution, for two different geometries, for a rupture initiated along the San Jacinto Fault and propagates onto the San Andres fault. We use a slip weakening distance of 0.6 m (1st column) and 0.3 m (2nd column).