This research is to investigate the factors that control the localization of moment release at subduction zones. By comparing the positions of maximum moment release between subduction zones with different characteristics and correlating them with a variety of subduction zone parameters, information on the physical processes that influence the localization of moment release will be revealed. Determination of whether earthquakes of very different magnitudes rupture the same regions on the plate interface is important in understanding the role that fault strength plays in the localization of moment release. Since great earthquakes account for the majority of moment release at subduction zones, their influence on seismic behavior is essential to understanding the localization of moment release. This research is a component of the National Earthquake Hazard Reduction Program.