Effects of gouge fragment shape on fault friction: New 3D modelling results

The friction of granular fault gouge plays an important role in governing the mechanical behavior and hence earthquake potential of faults. Using numerical modelling, significant progress has recently been made towards understanding the micro-mechanics that drive fault gouge evolution. Despite these insights, many previous numerical models have predicted unrealistically low macroscopic frictional strength. Here we describe modified 3D discrete element simulations of fault gouge evolution. Our particle-based simulations, modelled on laboratory experiments, include breakable bonds between individual particles (or particle clusters) allowing fracture of aggregate grains. With accumulated strain, grains break up, evolving in size and shape to produce a textural signature reminiscent of natural faults. Cluster-simulations, producing pseudo-angular daughter fragments yield realistic frictional strength (0.6). Non-cluster simulations, producing angular and spherical daughter fragments, have much lower friction levels. We therefore demonstrate that gouge fragment shape and resulting interactions dominate the frictional strength of faults. Citation: Abe, S., and K. Mair (2009), Effects of gouge fragment shape on fault friction: New 3D modelling results, Geophys. Res. Lett., 36, L23302, doi: 10.1029/2009GL040684.