Earthquake Cycles in Fault-Bend Folds

Abstract

In fold-and-thrust belts and accretionary prisms, fault bends induce folding in the hanging wall that can alter the long-term loading rate on the megathrust and profoundly influence earthquake-related processes. To understand the impact of nonplanar faults and off-fault deformation on the seismic cycle, we incorporate fault-bend fold theory into fault dynamics and develop two-dimensional numerical simulations of slip evolution under a physics-based rate- and state-dependent friction law. Fault bends can play an important role in earthquake segmentation as a result of nonlinear fault dynamics, affecting the initiation and termination of earthquakes and the details of long-term interseismic behavior. Shallow earthquakes that initiate, propagate, and terminate near the surface are facilitated when the stratigraphy within incoming thrust sheets is not parallel to the underlying fault, as this can change the loading rate across the fault bend.