This research is proposed as an Accomplishment Based Renewal based on the strength of the past research of the proposer. Future work will continue to concentrate on the factors that control a major earthquake's size, location, and timing. Using plate tectonics as a framework, measurements will be made of the depth extent and geometry of the seismogenic zone, i.e., that portion of the plate interface capable of generating large earthquakes. The methodology developed to perform this measurement is innovatively flexible and powerful with rigorous statistical error estimates. Measurements will also concentrate on the "inside" part of the earthquake where spatial heterogeneity in coupling strength along the fault controls many features of seismicity and earthquake rupture processes. This research is a component of the National Earthquake Hazard Reduction Program.
