During slip on faults, sliding surfaces are worn and a layer of ground rock, or fault gouge, accumulates. Laboratory experiments indicate that gouge can change fault properties such as friction, sliding stability, and strength. An understanding of the evolution and state of these properties is essential for quantitative understanding of faulting processes. The P.I.s will conduct a numerical study using a variant of the discrete element method: in this model the bulk properties of a sheared layer of grains are the consequence of discrete interactions between many individual grains. They will investigate the relations between apparent friction and yield stress, and interparticle friction, normal stress, dilatancy and slip velocity in sheared gouge. They will also explore the temporal and spatial evolution of gouge and process zones (e.g. evolution of roughness and grain-size distributions) and the mechanics of slip localization.
