This research involves a continuation of the study of seismicity in coupled subduction segments and their surroundings (overriding plate, sea floor and subducting slab) to understand the strength and heterogeneity of coupling along the thrust interface. Specific areas of investigation are: 1) investigation of the relations between heterogeneous seismic coupling along the main thrust zone and seismicity in the sea floor and upper plate areas; 2) explanation of seismicity in the descending slab at intermediate depths and its relation to coupling; 3) correlation of seismicity with changes in a Coulomb measure of stress change (shear minus friction coefficient times normal stress change) in a subduction zone and its vicinity; and 4) investigation of compressional earthquakes in zones near the trench and towards the outer rise as signals of the maturity of the earthquake cycle of the thrust interface. This research is a component of the National Earthquake Hazard Reduction Program.
