Session I :
Micro-physics underlying earthquake nucleation and frictional behavior of complex fault zones : observations and simulation

2nd ACES (APEC Cooperation for Earthquake Simulation) Workshop in Japan

Anatomy of a slip event in an idealized fault gouge
David Sparks, Einat Aharonov


Two-dimensional numerical simulations of shear in a layer of frictional grains were conducted to illuminate the micromechanics of deformation in granular materials (such as layers of fault gouge) during "stick-slip" motion. We found that, while the largest intergranular forces in the system are between sets of grains aligned with the direction of maximum compression ("force chain grains"), the triggering mechanism for a slip event may reside in the grains that lie between force chains. As stress on the system increases, the "weak" contacts that are not in force chains accumulate enough shear force to reach the frictional sliding limit, while the force chain ("strong") contacts never reach this limit. It is suggested that when enough of the non-chain grains can frictionally slide, this material fluidizes, which destabilizes the force chains.

PDF (65KB) |