Characterization of stick-slip dynamics in granular fault gouge using the combined finite-discrete element method

摘要

Sheared granular layers undergoing stick-slip behavior are broadly employed to study the physics of earthquakes. Here, a two-dimensional implementation of the combined finite-discrete element method (FDEM) is used to explicitly simulate a sheared granular fault system including both gouge and plate, and to investigate the influence of different normal loads on macroscopic friction coefficient, kinetic energy, gouge layer thickness, and recurrence time between slips. In the FDEM model, the deformation of plates and particles is simulated using the FEM formulation while particle-particle and particle-plate interactions are modeled using DEM-derived techniques. The simulation results show that with increasing normal load, (i) the kinetic energy of the granular fault gouge system increases; (ii) the gouge layer thickness shows a decreasing trend; and (iii) the macroscopic friction coefficient does not experience much change. Analyses of the slip events reveal that, as the normal load increases, more slip events with large kinetic energy release and longer recurrence time occur, and the magnitude of gouge layer thickness decrease also tends to be larger. The simulations not only reveal the influence of normal loads on the dynamics of sheared granular fault gouge, but also demonstrate the capabilities of FDEM for studying stick-slip dynamic behavior of granular fault gouge systems.