Project Abstract
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We have made significant progress in understanding the mechanism of creep events on the SHF. A widely accepted model [Scholz, 1998] suggests that shallow slow slip events on strike-slip faults result from a conditionally stable zone near the top transition from stable to unstable zone (Model A in Figure 1). However, through numerical simulations, we demonstrated that such a model couldn’t explain both the rapid afterslip and the creep events recorded by a creepmeter following the 1987 Mw 6.6 Superstition Hills (SSH) earthquake. In contrast, we found that models which included significant heterogeneity in the shallow frictional properties of the fault, which is probably caused by fine-scale lithological variations, can be consistent with both the afterslip and interseismic creep events observed on the SSH fault. A manuscript on our results, coauthored with Yajing Liu and Yoshi Kaneko, is currently under review at Nature Geoscience. We have also made progress on understanding the triggering mechanism of creep events by nearby earthquakes. We add realistic static and dynamic stress perturbations to the 1D model we have built. The simulations show that static stress perturbations in the effective normal stress can advance or delay creep events. The magnitude and timing of stress perturbations determine the clock change of creep events. Dynamic stress perturbations in effective normal stress can advance the timings of creep events when the perturbation temporally decreases the effective normal stress. Perturbations that increase effective normal stress do not affect the timings of future creep events. |
