Pulse-like ruptures, seismic swarms, and tremorgenic slow-slip events with thermally activated friction

Abstract

The evolution of frictional resistance on a fault affects the characteristics of seismic ruptures. A wide range of rupture styles, from slow-slip events to fast earthquakes, can be explained under the isothermal rate- and state-dependent friction framework. However, laboratory experiments indicate that friction also depends on temperature, with a largely unknown impact on rupture patterns. Here, we explore how thermally activated friction affects rupture behavior in quasi-dynamic models of seismic cycles with a single velocity-weakening, temperature-strengthening asperity, whereby frictional healing occurs behind the rupture front due to shear heating. A transition from crack-like to pulse-like rupture propagation with self-healing fronts occurs as the temperature strengthening effect increases, spontaneously inducing steady, decaying, or growing pulses. With increasing activation energy, the cycle turns into earthquake swarms and tremorgenic slow-slip events, both characterized by strong interactions between slow and fast ruptures. The temperature sensitivity of friction may contribute to the natural complexity of the seismic phenomenon, potentially explaining a much wider spectrum of rupture behaviors and recurrence patterns.