Effects of Focal Mechanisms, Fault Slip, and Strain Rate on Earthquake Clustering

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Models to describe the relationship between earthquakes, faults, and tectonic strain generally three different types: those based on (a) seismicity,(b) faults, and (c) geodetically or geologically observed strain rates. Seismicity-based models often rely only on past earthquake data, ignoring fault information completely. Fault-based models generally apply only to earthquakes on pre-identified faults, either singly or in combination. Strain-based models assume that earthquake rates are related to some form of strain rate. They generally assume that earthquakes can occur anywhere, although strain based models may use fault slip information to infer strain rates. While hybrid models exist, they generally assume that future large earthquakes will occur on pre-identified faults. Many existing models show modest skill, but none includes fault properties, fault history, stresses from large and small earthquakes on and off of known faults, earthquake triggering, and tectonic strain accumulation. In this project the researchers will construct short-term and long-term models of earthquake interactions including all of the above effects.Their models of temporal clustering would be based on the Omori law of aftershock delay times, modified to account for the observed loss of detection capability for early aftershocks of large earthquakes. Their models would have several adjustable parameters, which would be optimized for best fit to earthquake data according to a likelihood criterion. They would then formalize the model as a forecast to be tested in the Collaboratory for the Study of Earthquake Predictability (CSEP) program.