SCEC Award Number 21154 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Is topography part of the “key” in the Cajon Pass earthquake gate? Continuing study with realistic and synthetic models
Investigator(s)
Name Organization
Christodoulos Kyriakopoulos University of Memphis David Oglesby University of California, Riverside
Other Participants Baoning Wu, UC Riverside (Graduate Student)
SCEC Priorities 4a, 1e, 2e SCEC Groups FARM, SAFS, Seismology
Report Due Date 03/15/2022 Date Report Submitted 11/28/2022
Project Abstract
 This work is a continuation of the previously supported SCEC project #19223 and #20151.This proposal investigates the effect that topographic asymmetry has on the rupture propagation across the Cajon Pass in Southern California with more focus on super shear rupture and permanent normal stress effects. Our investigation is based on the use of 3D dynamic rupture models. We designed experiments that allow us to compare results between models with topography (realistic and synthetic) and models with a flat free surface. Although our work is focused on the Cajon Pass area, additional synthetic models allow us to draw more general conclusions that are applicable to other areas of the world and topographic effects in general. Results from previous proposals (#19223 and #20151) showed that the asymmetric topography of the San Gabriel and San Bernardino mountains interacts with earthquakes propagating along the SSAF. More specifically, we discovered that the asymmetric topography produces a pattern of clamping and unclamping of the fault near the earth's surface and this pattern moves along with the propagation of the rupture. When ruptures passes the CP the pattern of clamping-unclamping reverses.

Intellectual Merit Our work is relevant for at least three major areas of SCEC research. First, the collective effort to study and understand the Cajon Pass Earthquake Gate as a key area for the development of future large events in Southern California. Second, implementing and understanding the effects of realistic features in dynamic rupture models (4a, 4e). For example, in the specific case of southern California, the asymmetric disposition of the San Bernardino and San Gabriels Mountains around the Cajon Pass and the feedback between topography and the rupture front. Third, combining advanced numerical models and HPC to investigate and better understand earthquake rupture phenomena.


Broader Impacts The numerical results from our work on dynamic rupture models of the Cajon Pass, are used in combination with a virtual reality system in outreach and education events in the CERI Visualization Lab.
Exemplary Figure Figure 2. Permanent normal stress changes with and without topography for models with super shear rupture induced by free surface (S=1.0). (a) and (b) final slip distribution and permanent normal stress change around the CP observed in experiments with the “synthetic” topographic model. (c) and (d) final slip and permanent normal stress change for the “synthetic flat” model. Both models implement a vertical fault with no along-strike bends. A comparison between panels (b) and (d) reveals the effect of asymmetric topography on the final normal stress pattern.