Modeling of Stick-Slip Behavior in Sheared Granular Fault Gouge Using the Combined Finite-Discrete Element Method

TL;DR

This study uses a combined finite-discrete element method to simulate sheared granular fault gouge, revealing how normal loads influence seismic behavior, energy release, and gouge layer properties, aligning with experimental observations.

Contribution

The paper introduces a 2D FDEM simulation framework for granular fault systems, effectively capturing stick-slip dynamics and load-dependent behaviors not previously modeled in detail.

Findings

Seismic moment distributions match laboratory experiments.

Increased normal load raises kinetic energy and slip event magnitude.

Gouge layer thickness decreases with higher normal loads.

Abstract

Sheared granular layers undergoing stick slip behavior are broadly employed to study the physics and dynamics of earthquakes. Here, a two dimensional implementation of the combined finite discrete element method (FDEM), which merges the finite element method (FEM) and the discrete element method (DEM), 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 seismic moment, 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 simulated seismic moment distributions are generally consistent with those obtained from the laboratory experiments. In addition, the simulation results demonstrate that with increasing normal load, (i) the kinetic energy of the granular fault 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; while the macroscopic friction coefficient drop decreases. 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 systems.