Evaluation of parameter dependencies of AE accompanying sliding along a rough simulated fracture

Understanding shear slip behavior on fractures is indispensable for understanding earthquake mechanisms. In this study, we have investigated the characteristics of AE accompanying sliding along simulated fracture surfaces in an attempt to evaluate the dependencies of AE on sliding velocity and stress applied on the fracture. Our sliding experiments using pre-fractured granite specimens were conducted at room temperature and under a confining stress between 5 MPa and 20 MPa. Sliding velocity was kept constant during the experiments in the range of 1.15 .tm/s to 1155 gm/s. We evaluated the characteristics of AE by determining the m-value, which shows the statistical characteristics of AE. Evaluation of parameter dependencies of the m-values reveals that the m-values have little dependence on stress state on the fracture and that they have negative dependence on sliding velocity. The small m-value indicates that AE events with larger maximum amplitude occur. Therefore, our results imply that high sliding velocity has a tendency to generate higher energy AE events during the sliding. This suggests that the characteristics of braking or slip of asperities on the fracture during the sliding were affected by sliding velocity rather than stress on the fracture.