3D multiscale modeling of fault-slip rockbursts around deep tunnels: Insights into static versus dynamic triggering mechanisms

The occurrence of violent and destructive fault-slip rockbursts during deep underground excavations remains poorly understood and difficult to predict, due to their inherent multiscale complexity and the interplay of coupled physical processes, including seismogenic fault rupture, coseismic stress redistribution, seismic wave propagation, and fracture growth around the excavation. In this study, we develop a novel three-dimensional (3D) multiscale computational framework for modeling fault-slip rockbursts. The model is used to simulate an M w 2.88 seismic rupture along a 500 m-long normal fault, and further captures the resulting coseismic static and dynamic stress changes around a 10 m-diameter tunnel located 100 m away from the fault hypocenter. Simulation results show that the fault-slip event can trigger severe rockbursts, characterized by violent rock ejection and rapid energy release occurring approximately 0.17 s after the peak amplitude of seismic waves reaches the tunnel. This time lag reveals a dominant triggering mechanism driven by coseismic static stress changes, which has often been overlooked in favor of dynamic triggering effects associated with seismic waves. Sensitivity analyses of different earthquake magnitudes and tunnel-fault configurations further confirm the primary role of coseismic static stress perturbations in the near-field, especially within compressional quadrants of the mainshock rupture. These findings provide new mechanistic insights and establish a physic-based framework for assessing and mitigating rockburst hazards during deep underground excavations. • A novel 3D multiscale modeling framework is developed to simulate fault-slip rockbursts. • The model simultaneously captures large-scale fault rupture and small-scale crack growth. • Coseismic static stress changes drive fault-slip rockbursts in the near-field.