Geometrically controlled slow slip enhanced by seismic waves: A mechanism for delayed triggering

Abstract

Seismic waves generated during earthquakes induce transient stress changes in the crust. These ephemeral perturbations can trigger critically stressed asperities at remote distances, often with significant time delays. The physical mechanism that governs this phenomenon is not completely resolved. Numerical simulations of dynamic perturbations passing along a heterogeneous pre-stressed fault, demonstrate that weak portions of the fault that host ongoing slow slip can transfer stress in response to the perturbations, loading asperities poised for failure. We find that the magnitude of perturbation, the state of the asperity, as well as deformation of the surrounding material, jointly control the delay time between perturbation and triggered event. The slow-slip modulated delayed triggering model that we propose can account for the wide range of observed delay times in nature, including the two end-member cases of no delay and no triggering. Triggered slow slip events in nature might provide warning signs of impending earthquakes, underscoring the importance of high-resolution monitoring of active fault zones.