Effect of a low-velocity zone on a dynamic rupture

Abstract Dynamic-crack earthquake simulations generally assume that the crustal material surrounding faults is laterally homogeneous. Tomographic and near-fault seismic studies indicate that the crust near faults is instead comprised of rocks of varying material velocities. We have tested the effects of adding material-velocity variation to simulations of spontaneously propagating earthquakes. We used two-dimensional plane strain conditions coupled with a slip-weakening fracture criterion and examined earthquakes on faults that bisect finite-width low-velocity zones em-bedded in country rock and earthquakes on faults that bound two different-velocity materials. When a fault bisects a low-velocity zone, the normal stress remains un-changed, but both the rupture velocity and slip-velocity pulse shape are perturbed. The presence of the low-velocity zone induces high-frequency oscillations in the slip function near the rupture front. When the fault is on the edge of the low-velocity zone, the oscillations are more pronounced, and repeated sticking and slipping can occur near the rupture front. For the slip-weakening (velocity-independent) friction model, however, the temporary sticking does not lead to permanent arrest of slip