Mechanics, slip behavior, and seismic potential of corrugated dip‐slip faults

Abstract

To better understand the mechanics and seismic potential of nonplanar fault surfaces, we present results from a suite of numerical models of faults with sinusoidal corrugations in the downdip direction. Systematic variations in corrugation wavelength, amplitude, and loading angle are introduced to determine the effects on slip behavior and seismic moment release. We find that corrugated faults, in general, slip less than planar faults. Changes in slip behavior are nearly scale‐independent and are dominantly controlled by the amplitude/wavelength of corrugations. Model results suggest that obliquely loaded corrugated faults accumulate less strike slip than a planar fault with the same tip line dimensions and average orientation. This result implies that slip direction is not a reliable indicator of regional stress direction and may at least partially explain repeated, nearly pure dip‐slip coseismic events at oblique plate boundaries. Though the scalar seismic moment release is always less for corrugated fault surfaces due to a greater reduction in slip compared to increased surface area, for geologically reasonable corrugation geometries, changes in total scalar moment release are not significantly different than planar faults. Techniques that utilize highly simplified fault geometries may therefore accurately reproduce scalar moment release but will nonetheless incorrectly predict coseismic slip magnitudes and distributions, as well as regional stress orientations.