SCEC Award Number 12147 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Investigation of causes and effects of transient deformation on the Superstition Hills Fault with physics based model
Investigator(s)
Name Organization
Meng Wei Woods Hole Oceanographic Institution Jeff McGuire Woods Hole Oceanographic Institution
Other Participants
SCEC Priorities 5d, 5e, 2c SCEC Groups Geodesy, FARM, Seismology
Report Due Date 03/15/2013 Date Report Submitted N/A
Project Abstract
 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.
Intellectual Merit We improved our understanding of the friction and stress heterogeneity both in depth and along strike on the Superstition Hills Fault in the Salton Trough. As many physics based rupture simulations rely on the accurate knowledge of friction and stress distribution, our findings will improve the ability of physics based rupture simulations to actively predict near-fault ground motions for faults like Superstition Hills and Imperial Valley.
Broader Impacts Supported a young postdoc.
Exemplary Figure Figure 1. Two schematic models that may explain creep events on continental strike-slip faults such as the SHF. Model A is after Scholz [1998]. Model B is proposed to explain both rapid afterslip and frequent creep events. Following Scholz, the z axis is the stability parameter. In Model A, continuous creep arises from the stable zone and episodic creep originates from the conditionally stable zone. In Model B, continuous creep arises from layers 1 and 3, whereas episodic creep originates from layer 2.