https://doi.org/10.1029/2022JB025209

Understanding the response of a fault gouge, the granular material at the core of fault zones, can shed light on the way earthquakes are nucleated. For this purpose, in this paper, a series of particle-based simulations of a fault gouge, under conditions similar to the ones expected at deep down at the seismogenic zone, are conducted. A full scale fault with dimensions of the order of kilometers is almost impossible to be simulated at the grain-scale. In order to capture the inhomogeneities at this level, the response of several, small samples is combined in a stochastic-ensemble manner. The results suggest that local stick-slip events are vanishing with increasing number of tests thus, they are not critical for the macroscopic, global, material’s response. Contrary to this, the amount of slip needed to promote earthquake instabilities is shown to vary with respect to the mean particle size of the material. Finally, the granular polydispersity and the slip velocity do not seem to affect the system’s behavior. The later highlights possible important role of multiphysics on the rheology of fault gouges and provides evidence for the constitutive assumptions used in continuum models.