Effects of near-fault stress evolution and surface asperities on rough fault slip: An evaluation based on photoelastic shear tests and additively printed models

Abstract

Fault slip due to resource excavation activities is a potential cause of earthquakes and rockbursts; its fundamental cause is the redistribution of the near-fault stress field. Knowledge of the distribution and evolution of full-field stress around natural faults is crucial to revealing the mechanisms of fault slip. However, natural faults are rough and numerous asperities on their surfaces lead to stress heterogeneity, which makes quantifying the distribution and evolution of near-fault stress challenging. In this study, we explored the distribution and evolution of full-field stress in rough faults using photoelastic analyses of direct shear tests involving three-dimensional printed fault models. The near-fault shear stress and secondary principal stress difference (SPSD) in the printed fault models under various shear loads were quantified, the distribution and evolution characteristics of near-fault stresses were analyzed, and the influences of asperities on near-fault stress evolution were addressed. Our findings indicate that numerous stress concentrations form near the upslope segments of asperities during fault slip. Near-fault shear stress and SPSD present a high similarity in concentrated stress distribution and evolution. It is more effective to characterize the effect of surface asperities on the slip of rough faults using SPSD drops than using shear stress drops. The sequence of local SPSD drops is closely related to the area enveloped by uphill fault slope curves, which facilitates the prediction of earthquake nucleation. Our study provides a basis for characterizing the effects of near-fault stress and surface asperities on the slip of natural rough faults.