A brief review on the role of aseismic slip on experimental faults: Implications for fault-involved geological engineering safety

Abstract

Faults exist at various depths within the upper crust at different scales, and its shear failure can occur in numerous geological engineering scenarios, posing threats to engineering safety and environmental sustainability. Aseismic slip is ubiquitous throughout the fault slip process, while its role on the fault mechanics remains to be better understood. Here we briefly present a comprehensive and critical review aiming at explaining the role of aseismic slip on the earthquake cycles reproduced on experimental faults under well-controlled laboratory environments. We first introduced the rate and state frictional law, the most widely used constitutive law derived from laboratory for modeling friction evolution and quantifying the fault slip behavior. Three typical experimental setups including the direct shear experimental setup, double direct shear setup, and triaxial shear setup are introduced. We then reviewed the role of aseismic slip on the initiation, propagation, and termination of fault ruptures. Specifically, we elucidated that the aseismic slip has close relationships with spatiotemporal stress redistribution, nucleation phase, energy dissipation, fault zone heterogeneities, fluid dynamics, and stability transitions of the macroscopic fault. This review shows that the previous experimental studies partially deciphered the physical mechanism of the whole faulting process, and recent advances provide complementary insights. However, open questions in multiple aspects mentioned above are still challenging and remain to be addressed by future experimental studies. We proposed possible perspectives to be explored in the future, such as fluid dynamics, fault zone heterogeneities, and scaling to natural faults, which could allow a better understanding of fault mechanics and earthquake source processes by advancing related laboratory experiments. Such an advanced understanding of fault aseismic slip will ultimately contribute to safely implementing numerous fault-involved geological engineering activities and guaranteeing environmental sustainability.