Intersected Structure and Superpose Tectonics between the Eastern Margin of Japan Sea and the Toyama Trough, central Japan

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This study had conducted geomorphologic survey utilizing multi-narrow beam swath bathymetry and acoustic imaging by side scan sonar and sub-bottom profiler in the Japan sea-area, As the results the following were elucidated (1) The Pliocene and later folding and related fracturing had developed surfacial layers of methane hydrate as shallow as the uppermost layer is outcropped on the sea bottom to be observed by the submersible vehicle. It was assured that hydrate domes similar to salt domes have been formed on structural highs where migration and upwelling of methane are localized along the anticline axes.On land, we have continued our GPS geodetic monitoring of the present-day ongoing crustal deformation. The results confirmed the distribution of active faults across both regions in land and sea, and also intersecting relationships among them. Our seismo-geological surveys on the Atotsugawa fault system, one of the most active faults in Japan, made clear that the eastern-half segment of seismogenic faults had also been activated at the latest event in 1858 as well as the western, suggesting the deep intersection of basement structure in a N-S trend and NE-SW trending weak zone called the Niigata-Kobe tectonic belt.In order to resolve the dynamics of intersection, we will promote an integrated comprehensive study among geophysics, geodesy, geology and other material sciences on the mechanical relationship between tectonic phenomena and those in the lower crust beneath seismogenic zone. In 2008 and after, we join the five-year research and monitoring program for the zone of tectonic strain concentration along the eastern margin of Japan Sea.