Fault asperities and the transition from aseismic creep to stick-slip: implications for earthquake precursors

Fault asperities significantly influence fault friction and stability, stress patterns and the nature of slip events. Response is contrasted for stress-reactivated laboratory faults both with and without asperities. Asperities contribute to fault strength, necessitating a longer distance for slip nucleation, and elevating the energetics of slip. Asperities result in a heterogeneous distribution of fault rupture manifest as slip pulses and variable-speed slip as aligned with the cascade failure model for earthquakes. These asperities on the fault surface act as both barriers and stress concentrators, influencing the initiation and progression of seismic events. Our findings suggest that the pre-seismic time window, modulated by an asperity, can serve as a critical indicator for fault slip forecasting. These insights into the mechanical behavior of asperities under different stress regimes enhance our understanding of fault slip dynamics, towards improving earthquake prediction and assessing seismic hazard.