A 3-D Seismic Investigation of the Sediment-to-Rock Transition and Its Relationship to Nankai Subduction Thrust Seismicity: U.S.-Japan Collaborative Program

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9730637 Bangs this award will support a seismic reflection, refraction and passive seismicity program to study underthrusting of oceanic crust along the Nankai Trough off the east coast of Japan. The primary feature to be examined in this experiment is the subduction thrust fault from its aseismic zone in the Trough (trench) to a depth of at least 15 kilometers beneath the continental margin where the thrust is marked by significant seismic activity. The goal of the study is to examine changes in physical properties along the thrust as it changes from aseismic to seismic expression. Understanding this transition from compaction and aseismic slip to brittle failure is a major unknown in understanding lithospheric consumption and earthquake dynamics. This Nankai seismogenic zone marks the location of major destructive earthquakes along the Japanese margin. The project is a collaborative experiment. United State scientists will be responsible for acquiring and interpreting 3-dimensional seismic reflection data from the thrust fault and accreting margin. Japanese colleagues will be responsible for deploying ocean bottom seismometers for seismic refraction and passive seismicity studies. In addition t the basic scientific interpretation to be derived from the data, the experiment is critical to the development of the MARGINS initiative and will provide necessary site location data for future drilling by the international Ocean Drilling Program. ***