Insights to slip behavior on rough faults using discrete element modeling
Fournier, Thomas; Morgan, Julia
 We simulate a range of fault slip behaviors using the discrete element method (DEM) to examine the controls on different slip modes on rough faults. Shear strain is imposed upon a 2-D bonded particle assemblage that contains a predefined fault. Slip modes on the fault vary from creep, to slow-slip, to stick-slip behavior, both spatially and temporally. The mode of slip is controlled largely by the local stress field along the fault, which depends on the local fault roughness. Portions of the fault that fail in relatively low normal stress regimes tend to slide continuously, whereas areas with high clamping stress produce stick-slip events. During stick-slip events, regions within the rupture zone that experience high slip are associated with physical asperities on the fault; ruptures terminate at barriers and through dissipation of the stored elastic energy. The simulated events show stress drops between 0.2–50 MPa, a slightly larger range than is inferred for natural earthquakes. Simulated events also have higher slip magnitudes than are observed during earthquakes for a given rupture length. The simulation produces many characteristics of fault behavior and is shown to be a successful avenue for future studies on the mechanics of fault slip.