SEMINAR - Nadia Lapusta

Insights from modeling long-term slip histories of faults governed by
laboratory-derived friction laws

Nadia Lapusta
Mechanical Engineering and Geophysics
California Institute of Technology

Wednesday, October 31st, 1:00pm GMCS 422

We have been developing methodology that allows us to simulate long histories of seismic and aseismic fault slip while accounting for slow tectonic loading and all inertial effects. Our 3D models incorporate laboratory-derived rate and state friction laws. We have used 3D models to simulate interaction of seismic and aseismic slip, to reproduce abnormal scaling of moment and recurrence time for small repeating earthquakes, and to study interaction of dynamic rupture with fault heterogeneities over many earthquake cycles. In 2D models, additional dynamic weakening mechanisms due to shear heating are incorporated, When combined with defect regions to nucleate ruptures, fault models with high static friction strength and low dynamic strength operate under low average shear stress and low heat production, while producing earthquakes that have typical stress drops and pulse-like mode of rupture propagation. Hence the models reconcile several laboratory and observational constraints. Decrease in dynamic weakening causes the fault to operate at higher average levels of shear stress and results in systematic change of rupture mode from pulse-like to crack-like. Such change of dynamic rupture mode with fault prestress has been recently documented in laboratory experiments.