Abstract: Plate subduction margins have been the subject of various fields of geoscience research, such as tectonics / structural geology, seismology including Tsunami disaster, and hydrocarbon resources. Among a number of possible approaches, focus has been made to accretionary prism, the highly deformed (thrusted) geologic body formed above the subducting plate. This is because accretionary prisms are actively deforming, thus producing earthquakes and tsunamis, due to the plate subduction and show the structural styles as the result of the deformation history. Most of the hydrocarbon indicators have been identified in the accretionary prisms and their sedimentary covers, i.e. fore-arc basin and slope basin deposits.

The Nankai subduction margin is one of the most studied examples of the world, where the Philippine Sea Plate is subducting beneath the Eurasian Plate at a rate of 4 cm/year. The sediments upon the basaltic oceanic crust of the subducting plate mainly consist of hemipelagic mudstone. The overriding plate provides turbidite sequence of sandstone and mudstone. A décollement (the plate boundary) can clearly be identified within the hemipelagic mudstone as a reflection with reverse polarity. The sedimentary pile above this horizon is subject to be scraped and accreted to the edge of the Eurasian Plate. 

This presentation shows current understanding of the deformation process from seismic profiles, geologic modelling and a series of scientific drillings. It is to demonstrate how the Nankai subduction margin has dynamically been deforming and impacting on fluid flow and resources within the accretionary prism.

Bio: Yasuhiro Yamada is Director of R&D Center for Ocean Drilling Science (ODS) at Japan Agency for Marine-Earth Science and Technology (JAMSTEC). Previously, he worked for 16 years as an exploration geologist for JAPEX (Japan Petroleum Exploration Co.), and for 12 years as a professor at Kyoto University. Yamada's research interests include scientific drilling, geomechanics and structural geology. He has authored or co-authored more than 100 technical papers. Yamada holds a PhD in geology from University of London, UK.