This grant will continue studies of the geometry of fault gouge to explore the role of the particle distribution in the micromechanics of fault-zone instabilities. Previous friction data will be analyzed in an attempt to correlate the evolution of frictional parameters such as characteristic displacement and velocity weakening with comminution and the evolution of shear structures both within the gouge and at the wall-rock interface. These data will be supplemented by a second series of friction experiments, and detailed mapping of natural fault zones to search for analogous structures.
