SCEC Award Number 20151 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
SCEC Priorities 4a, 1e, 2e SCEC Groups FARM, SAFS, GM
Report Due Date 03/15/2021 Date Report Submitted 03/29/2021
Project Abstract
 This work is a continuation of the previously supported SCEC project #19223.
We are using dynamic rupture models to investigate the effect of the asymmetric topographic relief (San Bernardino and San Gabriels Mtns.) around the Cajon Pass, CA. Comparing results from models with flat and topographic free surface, we have found the the presence of the asymmetric topography generates normal stress perturbations that are visible near the rupture front and the free surface. For example, for ruptures with nucleation location south of the Cajon Pass and south to north propagation, we observe a concentration of normal stress increase (clamping) ahead of the rupture front and a concentration of normal stress decrease (unclamping) behind the rupture front. This pattern is inverted when the rupture passes the Cajon Pass and the topography switches side (from the San Bernardino to the San Gabriels Mtns.). The same is valid (including the inversion of the normal stress pattern) in models with nucleation location north of the Cajon Pass and north to south propagation. Finally, we have complemented our investigation with synthetic topography models that help us clarify on the mechanism(s) driving the normal stress changes and proceed with simulations that include super-shear rupture.
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 3
Figure 3. Synthetic topographic model and schematic explanation of normal stress change. Normal stress changes for simulation with nucleation north of the Cajon Pass. Panels (a) and (b) show normal stress changes at t = 10 s and t = 45 s respectively. Dashed circles circumscribe the area near the rupture front and the topographic normal stress change. (d) Schematic representation of a right lateral strike slip fault with asymmetric topography to the right (1) and to the left (2) with respect to an observed moving with the rupture front.