Evolving seismic asperities by velocity- and temperature-dependent friction

Binhao Wang, & Sylvain D. Barbot

Submitted August 30, 2026, SCEC Contribution #15253, 2026 SCEC Annual Meeting Poster #TBD

Seismic asperities are widely treated as fault patches with fixed velocity-weakening friction, a material property frozen in time, implying a static separation between coseismic and aseismic slip. However, in nature the same fault regions can host both seismic ruptures and postseismic afterslip, and that geodetically locked area can shrink before large earthquakes, implying temporal evolution of seismic asperities. Laboratory experiments show that rock frictional stability depends on both slip velocity and temperature. Because slip velocity and temperature vary widely over an earthquake cycle, a fault can therefore traverse regimes with different frictional stability. Here, we test whether such evolving friction behaviors observed in laboratory experiments naturally explain the temporal evolution of seismic asperities. We conduct fully-dynamic earthquake cycle simulations using a physics-based friction law that captures the multiple-regime frictional behavior shared by many natural rocks and fault gouges by the competition between rate-dependent brittle flow and thermally activated ductile creep. In our simulations, seismic ruptures penetrate transiently below the base of the seismogenic zone as the large velocity excursion at the rupture front shifts the deep fault into a velocity-weakening state. During postseismic relaxation, the deep fault remains hot, rejuvenated, and stressed above steady state, sustaining velocity-strengthening afterslip within regions that hosted coseismic rupture. Over the interseismic period, the same velocity dependence erodes the locked area, so the time-averaged geodetically locked area is smaller than the region that ruptures seismically. All three behaviors emerge from a single physical mechanism without imposed heterogeneity in constitutive parameters, highlighting that seismic asperities can evolve dynamically, with boundaries that migrate throughout each earthquake cycle.

Key Words
asperity; rock friction; afterslip; precursor; locked; creep

Citation
Wang, B., & Barbot, S. D. (2026, 08). Evolving seismic asperities by velocity- and temperature-dependent friction. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)