Project Abstract
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Most inversions consider the depth distribution of interseismic fault slip-rate to be time invariant. However, some numerical simulations show penetration of dynamic rupture into regions with velocity-strengthening friction, with subsequent interseismic up-dip propagation of the locked-to-creeping transition. We explored this hypothesis by developing and testing crack models to describe creep penetration upward into the locked region. Previous work from Bruhat and Segall (2017) developed a new method to characterize interseismic slip rates, that does not assume that the spatial distribution of interseismic slip is stationary. This simple model considers deep interseismic slip as a crack loaded at specified slip rate at the down-dip end. It provides analytical expressions for stress drop within the crack, slip, and slip rate along the fault.
This work extended this new class of solution to strike-slip fault environment. Unlike Bruhat and Segall (2017) which considered creep propagation in a fully elastic medium, we included here the long-term deformation due to viscoelastic flow in the lower crust and upper mantle. We improved the model presented in Bruhat and Segall (2017) to account for the coupling between creep and viscoelastic flow, and derived expression for viscoelastic response due to time-dependent creep. Finally, we employed this model to investigate the long-term rates along the Carrizo Plain section of the San Andreas fault. |