9315055 McCaffrey This research is to continue seismological investigations of Sumatra through analysis of data from a digital seismograph network that has been operating around the Sumatra fault and Toba caldera in northern Sumatra since October, 1990. The maximum depth and depth distribution of seismic failure on the Sumatra fault, the relation of the earthquakes and their fault plane solutions to geologic structures, the seismic velocity structure and attenuation beneath the fault and Toba caldera, and the relationship of the subducted slab and a possible tear within it to surface tectonics will be studied. The seismic network operates within a GPS geodetic network operated by Rensselaer and Scripps and provides the opportunity to study the spatial and temporal relations between seismic activity and geodetically measured strain. The work is being done in cooperation with the Indonesian Meteorological and Geophysical Agency (Jakarta) who operate the seismographic networks in Indonesia. This research is a component of the National Earthquake Hazard Reduction Program. ***
