SCEC Award Number 13035 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 University of Rhode Island Jeff McGuire Woods Hole Oceanographic Institution
Other Participants
SCEC Priorities 5, 5, 2 SCEC Groups FARM, Geodesy, GMP
Report Due Date 03/15/2014 Date Report Submitted N/A
Project Abstract
 We have made progress on understanding the triggering mechanism of creep events by nearby earthquakes. We first built a database of dynamic and static stress perturbations to the Superstition Hills Fault from real earthquakes that have a known creep response (or lack thereof) from creepmeter, InSAR, and/or field survey data. There is considerable variability in the existence, amount, and along-strike variations in creep events triggered by regional, moderate to large earthquakes. Our dataset spans this variability and has well-documented creep responses. Secondly, we simulated the triggering process by adding realistic static and dynamic stress perturbations to the fault rupture model we have built. The simulations show that static stress perturbations can advance or delay creep events, whereas dynamic perturbations are more effective in triggering than delaying creep events. The magnitude and timing of the modeled perturbations determines the clock change of creep events. The magnitude and interval of modeled creep events changes permanently after static stress perturbation but only for a short period after dynamic perturbations. The Landers, Hector Mine, and El Mayor earthquakes dynamically triggered creep events on the Superstition Hills Fault. The size of triggered slip increases as the dynamic perturbation increases in the direction of unclamping, whereas the scaling is consistent with observations. The most surprising result is that flipping a waveform can reverse the direction of clock change, which indicates that the polarity and incoming angle of waveforms are important factors in triggering creep events.
Intellectual Merit We have made progress on understanding the triggering mechanism of creep events by nearby earthquakes. We first built a database of dynamic and static stress perturbations to the Superstition Hills Fault from real earthquakes that have a known creep response (or lack thereof) from creepmeter, InSAR, and/or field survey data. Secondly, we simulated the triggering process by adding realistic static and dynamic stress perturbations to the fault rupture model we have built.The simulations show that static stress perturbations can advance or delay creep events, whereas dynamic perturbations are more effective in triggering than delaying creep events.The most surprising result is that flipping a waveform can reverse the direction of clock change, which indicates that the polarity and incoming angle of waveforms are important factors in triggering creep events.
Broader Impacts Our results will improve our understanding of the mechanics of the shallow portions of faults, which has significant implications for the shaking/hazard levels expected from future earthquakes in the Salton Trough, an agriculturally and economically important area.
Exemplary Figure Figure 1. Slip history on the Superstition Hills Fault between 1988-2011. Blue lines are from creepmeter data. Green line is from InSAR observations. Black solid line is a model based on Wei et al. [2013]. Grey bars show the time constraint on that particular creep event by InSAR. Three creep events were triggered by Landers, Hector Mine, and El Mayor earthquakes.
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