This research consists of a joint observational and theoretical investigation of the spatio-temporal pattern of earthquake aftershocks. This will be a test of the critical point model in which, on a plate boundary scale, the crust is not in a continuous state of self-organized criticality but repeatedly approaches and retreats from the critical state. Evidence for this includes the power law increase in regional activity observed to precede many large events and the regional quiescence, which follows. The power law increase is sometimes modulated by a log-periodic fluctuation. If the critical point model is a valid representation for seismicity, then power law scaling should also be observed in the aftershock sequence following large events. This is seen in the form of Omori's Law. The results should improve understanding of the physical origin of log periodic fluctuations and the relationship between the critical point model and other recent theoretical models of aftershocks, which also yield Omori's Law. This research is a component of the National Earthquake Hazard Reduction Program.
