Stick-slip failure in heterogeneous sheared fault with a variety of fault roughness

Abstract

Stick-slip failure, as a possible mechanism for destructive shallow focus earthquakes, often occurs in heterogeneous faults. To investigate the physical processes of stick-slip failure in heterogeneous faults, direct shear tests are performed in the laboratory, combined with the use of multi-channel high-speed dynamic strain acquisition system, on the bimaterial samples. The bimaterial samples consist of PMMA (poly methyl methacrylate) and PC (poly carbonate). This experimental study is concerned with the effects of fault roughness on the stick-slip behaviors along the heterogeneous faults. The metallographic microscope is used to quantitatively measure the surface morphology of the heterogeneous faults. The stress distribution along the simulated fault is highly non-uniform, which dictates the initiation locations of stick-slip failure. The nucleation starts at a firstly-yielded material point, and as the energy accumulates in the heterogeneous fault, the nucleation zone is progressively formed. The crack tip propagates at an increasing velocity until the entire fault is penetrated. It is found that a rougher fault is corresponding to a slower rupture velocity, a smaller local stress drop, a larger critical slip-weakening displacement, and a larger critical crack length.