［Abstract］ 　Subduction zone is characterised by great earthquakes along the plate boundary. In order to understand the dynamics of precise plate subduction, our researches includes three following themes: 1) Quantitative studies of structures of deep seated accretionary masses and physical properties of their rocks, reaction processes of minerals, migration process of water. 2) Experimental and theoretical studies on mechano-chemical processes of plate-boundary rocks, failure - recovery process, and 3) Detail studies of ocean drilling cores logged by newly designed riser - drilling vessel which is now developing and constructing to reveal the substance of subduction boundary and seismogenic zone. ［Research object］ ［Seismogenic zone］ (1) The pseudotachylyte, the typical fault rock of the seismic rapid slip, is found in the Cretaceous Shimanto accretionary complex, onshore extension of the present Nankai subduction zone. (3) The evidence for the repeated seismic slip. Newer pseudotachylyte injection vein cuts the older one. The repeating slip is the one of the important feature of the seismogenic fault. (2) The fault rock is composed of the clast of the host rocks, pseudotachylyte and the vein minerals. This indicates the active fluid flow along the fault zone. ss : sandstone, qz: quartz, PS: pseudotachylyte. ［Shallow portion］ (1)Imbricate structure in the Shimanto accretionary complex. Note that liquefied layers (black arrows) are repeated three times. (2) JOIDES Resolution, a drilling vessel of Ocean Drilling Program. (3) Core photograph of the plate boundary decollement zone at the toe of Nankai Trough accretionary prism. (4) Secondary mode SEM image of fault breccia in the d ec ollement zone. Random and preferred orientations of clay minerals characterize interior and margin of fault breccia,respectively. (1) (2) (3) (4) ［Deep portion］ (1) Himalayan range and Yellow band Marine sediments of defunct Tethyan sea forms the roof of the world. (2) Folded Ryoke meta-chert Marine sediments are intensely folded during the plate subduction. (3) Distribution of mineral sealed cracks Fluids within the plate boundary rocks remains as mineral sealed cracks. They may perform reflections observed in the seismic profiles. (4) Chemical map of garnet: Chemical change in minerals offers the information to estimate the pressure-temperature condition during their growth. EPMA analysis on garnet (largest grain) show Fe increase from core (green) to rim (red) which implies increasing temperature during the growth. (1) (2) (3) (4)