Application of a Novel Local Dynamic Weakening Model Coupled with Smooth-joint Contact in the Simulation of Fault Ruptures and Laboratory Earthquakes

Abstract

Discrete-element-method (DEM) codes were developed in the field of rock mechanics. Compared to continuum codes, it has many advantages such as allowing larger grain displacements, detachment of grains, and simulation of discrete fractures. However, the disadvantage of DEM codes in the simulation of higher confining pressure triaxial tests were not previously discussed. In this study, we explored how the non-Dirac-delta distribution of contact forces controls the fault rupture initiation, and its impact on fault rupture propagation under high confining pressure. Based on the above study, a novel local dynamic weakening model was proposed and incorporated into the smooth-joint (SJ) contact model. The dynamic weakening model is tested with simulations of experiments conducted under high confining pressures. It is shown to be successful at reproducing realistic fault rupture behaviors, and the synthetic acoustic emission (AE) characteristics including magnitude-frequency relationships and fractal dimensions match those in the experiment.