A Method for Earthquake Cycle Simulations: Quasi-static Evolution to Dynamic Rupture
Abstract
The goal of our project has been the development of a time-stepping methodology to understand and simulate full earthquake cycles with multiple events on geometrically complex faults, with rate-and-state friction and off-fault plasticity. This framework requires numerical methods to advance the model over long interseismic periods using the quasi-static equations, and through dynamic rupture using the elastodynamic formulation. In order to handle geometric complexities and off-fault plasticity, a volume discretization is required. During the quasi-static phase, we neglect inertia and the system evolves due to slow tectonic loading. Once inertial effects become significant we switch to solving the equations of elastodynamics. This switching method has been implemented in 1D, taking large time steps through the interseismic period and much smaller time steps in order to fully resolve coseismic rupture. In 2D we have solved the quasi-static equations for the antiplane problem by imposing constant creep at the downdip extension of the fault, intended to capture the effect of slow loading during the interseismic period. We have concurrently begun to use 2D plane strain models with off-fault plasticity to approximate multiple earthquake ruptures on rough faults. The initial conditions prior to the first event are sufficient to immediately nucleate dynamic rupture. Once the rupture has terminated and slip velocity is sufficiently small, fault strength evolves according to the aging law and the system is loaded by a constant increment in shear stress in the medium. This incremental method is an easy implementation that allows us to generate earthquake cycles on rough faults, but it is an approximation in the sense that it may overlook effects such as creep and afterslip during an interseismic time step. For the time being it may be a useful tool for incorporating the basic effects of interseismic load accumulation and to study how heterogenous residual stresses affect subsequent ruptures. However, it will be important to see what additional effects are captured once we implement the quasi-static evolution on rough faults with off-fault plasticity via our switching method.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.S43C2267E
- Keywords:
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- 7209 SEISMOLOGY / Earthquake dynamics;
- 7290 SEISMOLOGY / Computational seismology