Submarine Topography and Geological Structure in the Northern Margin of the Philippine Sea Plate

Abstract

The Hydrographic Department has prepared nine profiles of multichannel reflection survey across the Sagami, Suruga and Nankai Troughs. An interpretation of these profiles is presented in this paper.
The Philippine Sea Plate is subducting beneath the Eurasian Plate along the Nankai Trough, and the hemipelagic sediments and turbidite wedge sediments in the trough are accreted to the landward slope of the trough, building accretionary prisms with imbricated structure. The forearc basin inside the outer ridge which is the highest crest of the uplifted accretionary prisms, has been buried by terrigenous sediments. The forearc basin is differentiated and its extent is reduced by the folding of sediments.
Three left lateral transcurrent faults parallel to the Suruga Trough suggest that they are relict but still active structures formed by the collision of the Philippine Sea Plate with the Eurasian Plate in the past.