The hunt for a universal friction law: a bristle-based rate and state dependent constitutive relation simulates high velocity rupture experiments, connecting fault friction across loading conditions

Abstract

During earthquake rupture the interface experiences a multi-staged frictional evolution, including initial strengthening, weakening, and healing. Measurements of these stages under realistic slip histories reaching co-seismic slip rates of meters per second are only fit by direct parameterizations without internal state variable dependence needed to simulate arbitrary slip-histories. Commonly used forms of rate-state friction based on low velocity, step-change experiments cannot fit high-velocity slip-pulse measurements. We introduce to the geophysics community ‘bristle-state’ friction models, developed by control-systems engineers to predict the frictional evolution during arbitrary stressing, especially transitions from static. To isolate the influence of friction, we assume the driving velocity is applied directly to the interface, allowing an analytical solution for state. Although designed for low velocity experiments, we show that the bristle-state form can fit high-velocity, non-trivial slip histories, suggesting adapted state dependent models could provide a path towards a universal constitutive law, connecting observations across loading conditions.