Asymmetric Topography Causes Normal Stress Perturbations at the Rupture Front: The Case of the Cajon Pass

Abstract

AbstractWe use 3D dynamic rupture simulations to discover a previously un‐described effect of asymmetric topography on the earthquake process. With the Cajon Pass along the San Andreas Fault as an example, we find that asymmetric topography generates an alternating normal stress perturbation around the rupture front, near the free surface. When topography lies to the right of the propagating right‐lateral front, the normal stress perturbation is clamping ahead of the rupture front and unclamping behind. When topography alternates to the left, the perturbation reverses sign. The process is analogous to the normal stress variations on dip‐slip faults. While this effect does not strongly affect rupture propagation and slip in our current parametrization, it requires explanation and exploration. An understanding of the normal stress perturbation due to asymmetric topography will help prevent its misattribution to other sources and lead to a better understanding of the interplay of multiple processes during earthquakes.