Mechanisms of Slip Weakening and Healing in Glass at Co-Seismic Slip Rates

Abstract

The determination of co-seismic slip resistance in earth faults is critical for understanding the magnitude of shear stress reduction and hence the near-fault acceleration that can occur duringearthquakes. Knowledge of shear resistance dependency on slip velocity, slip distance, normal stress, and surface roughness is fundamental information for understanding earthquake physics and the energy released during such events. In the present study plate-impact pressure-shear friction experiments were employed to investigate the frictional resistance in soda-lime glass at relevant normal pressures and co-seismic slip rates. Detailed atomic force microscopy (AFM) and scanning electron microscopy (SEM) studies were carried out to understand the microstructures formed during the sliding process.The results of the experiments indicate that a wide range of frictional slip conditions exist at the slip interface. These slip conditions range from no-slip followed by slip weakening, strengthening, and then seizure for the case of glass-on-glass experiments. The first-weakening (μ ~ 0.2) is most likely due to the thermal weakening induced by flash heating and incipient melting at asperity junctions, while the second-strengthening (μ ~0.4 to 1.0) is understood to be caused by coalescence and solidification of melt patches. These results can be used to provide an understanding of mechanisms during dynamic fault weakening, and also to establish the constitutive description for the slip behavior in geological materials that can be used in dynamic models of earthquake rupture.