Keywords:Suruga Bay, Senoumi Bank, Breaking gravel
Senoumi bank (SB) is located in the central part of Suruga bay. A Suruga trough exists on the east side of SB and forms the border of Philippine Sea plate and the Eurasia plate. And SB has a major axis in the northeast - southwest direction, and a steep slope develops on the east side, and gentle slope develops in the west. On the east side steep slope of the SB, some topography conversion point exists, and forms the stepped slope. These stepped slopes resemble the topography that is characteristic of the subduction zone landside slope. We sampled the rock of several points in this steep slope. We succeeded in collection in a large quantity of gravel (pebble to cobble size) samples and mudstone samples. 95% of these a large quantity of pebble samples were the sedimentary rock (black-shale, sandstone, mudstone, etc.) origin, and it was estimated that these stones were supplied from Abe river or Ohi River. Furthermore, it was confirmed that 90% of gravels were crushed like the next type from 1) It is broken while leaving the shape of the rounded gravel for a part, 2) very angular shaped breccia, to 3) pebble sample with jigsaw crack on the surface. From image data provided on a SB eastside slope, many crushed rock outcrops are confirmed. It is estimated that these a large quantity of break gravel sample were formed by dislocation movement with thrust activity around the subduction zone.