Evolutionary patterns of shear behavior and crack distribution during fault slip

Abstract

Near-fault mineral resource excavation activities have the potential to induce fault slip, leading to the occurrence of earthquakes. This study explores the effects of dip angle and confining stress on the fault slip process caused by mining stress adjustment indoor tests and numerical simulations. It reveals the evolutionary patterns of shear behavior and crack distribution during the fault slip process. The results indicate that similar to shear stress, the acoustic emission activity associated with fault slip under mining stress exhibits distinct phase characteristics: A few cracks are randomly distributed in the linear steady stage → Isolated crack points cluster gather near the fault in the nonlinear steady stage → Cracks, mainly shear cracks, propagate along the fault in the meta-instability stage → Tension cracks connect shear cracks to propagate perpendicular to the fault in the instability stage. Generally, the fault slip process is governed by shear failure, accounting for over 75 %. Dip angle and confining stress significantly affect the shear behavior and crack distribution during fault slip. The constraint effect of confining stress causes intermittent slip of faults. An inverse relationship exists between peak stress intensity, the number of cracks, and the area impacted by shear slip and the dip angle. Accordingly, this research proposes support measures for areas at potential slip risk on faults, considering slip mechanical conditions and crack distribution characteristics. These results offer a method for identifying different stages of fault slip based on crack propagation, providing theoretical support for the monitoring and early warning of mining-induced fault slip.