Japan

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Research: Convergent Systems

Trench-parallel deformation in the Nankai accretionary prism, Japan

My research in Japan focuses on examinations of active and ancient structures associated with subduction off the southeastern coast of Japan. When studying active deformation, my collaborators and I use the SHINKAI 6500 submarine to study structures associated with the active Tokai thrust fault that are exposed on the seafloor in the Nankai trough. The results of our previous work suggests that the trends of first-order structures mapped during a survey of Tenryu Submarine Canyon reflect a significant amount of out-of-plane deformation is occurring along the Tokai thrust. This trench-normal structural fabric illustrates a large component of previously unidentified elastic strain, and suggests that faults cutting these folds may have significant strike-slip components. Our observations highlight a fundamental problem associated with ongoing studies of active subduction zones. Specifically, interpretations of structural relationships (and associated seismic hazard assessments) in provinces like the Nankai prism are often based upon seismic surveys and well data that lack the resolution to recognize fabrics like those identified in our study. For this reason, while much is known about the geodynamics of the Nankai prism, the finer details of individual structures remain largely unresolved.

In collaboration with

Nicholas Hayman, University of Texas, Austin

Kiichiro Kawamura, University of Yamaguchi

Ryo Anma, University of Tsukuba

Yujiro Ogawa, University of Tsukuba