Modeling supershear rupture in rocks

Supershear earthquakes represent one of the most hazardous rupture modes because rupture velocities exceeding the shear-wave speed can strongly amplify ground motion through Mach-cone-like wave focusing. The uploaded paper develops a two-dimensional hybrid FEM/peridynamic framework to study the transition from sub-Rayleigh to supershear rupture in both dry and fluid-saturated media. In this framework, peridynamics is used to model solid deformation, damage, and rupture propagation, while FEM is used to solve pore-pressure diffusion and fluid flow in saturated porous media. The model is validated against Homalite impact experiments and PMMA frictional-interface experiments, and then applied to dry and saturated fault-like media. A key finding is that dry media may exhibit either direct supershear transition or the Burridge–Andrews mother–daughter crack mechanism, whereas fluid-saturated media favor direct supershear transition due to poroelastic effects near the rupture front. The study also shows that pore-pressure perturbations can accelerate rupture propagation and allow rupture speed to approach the fast compressional wave speed in saturated media. However, several important limitations remain. The current simulations treat rocks mainly as linear elastic materials and use a linear slip-weakening friction law. Natural fault zones, in contrast, involve plastic yielding, permanent damage, rate- and temperature-dependent friction, heterogeneous permeability, evolving pore pressure, and complex fault-zone geometry. These processes may strongly influence rupture acceleration, supershear transition, off-fault damage, and seismic energy radiation. The proposed project will therefore extend the existing FEM/PD framework toward a more realistic poro-elasto-plastic and thermo-hydro-mechanical model for dynamic earthquake rupture in mature fluid-saturated fault zones.