Single-Asperity Friction and Wear in Seismic Faults: 2. DEM Simulations

Abstract

Seismic faults are rough, and their geometrical complexity is an important research topic. In this work, we present a numerical model dedicated to the simulation of friction and wear in an idealized fault asperity, taking inspiration from an experimental device used in a companion paper. The model can simulate the progressive damaging of the fault rock close to the contact, the release of fault gouge in the interface, and its circulation in the asperity and ejection from it. This allows to explore the complex interplay between a geometrical asperity and a gouge layer, in the presence of wear. Numerical results show that the asperity spontaneously evolves toward a tribological steady state in terms of friction, wear rate, roughness, and gouge thickness, in qualitative (and sometimes quantitative) agreement with experiments. We show that the existence of a geometrical asperity does not preclude the presence of a persistent gouge layer, which properties control the tribological response of the interface, and we emphasize the importance of understanding the mechanical, geometrical and rheological factors controlling its thickness.