A minimal model illuminates the physics behind pulse-like seismic
rupture and oscillatory slip rates in damaged faults
Abstract
Fault zones are often surrounded by a damage zone that exhibits lower
seismic velocities than the wall-rock, influencing earthquake
propagation and arrest. We present a one-dimensional minimal model of
frictional rupture, that approximates the elastodynamics of a fault
embedded within a low velocity damage zone. This model predicts two
families of steady-state rupture solutions: an overdamped regime,
describing a crack-like rupture, and an underdamped regime with
oscillating slip-rate in the wake of the rupture, which promotes
pulse-like dynamics. The minimal model contains two free parameters:
pre-stress on the fault, and seismic velocity reduction in the damage
zone. The 1D model results are validated by two-dimensional
elastodynamics simulations of earthquake rupture. We discuss the
applicability of our model results to natural observations, identifying
the preferred rupture style as function of structure of the fault zone,
and the geological consequences of oscillatory slip in the wake of
pulse-like ruptures.