Seismic reflection measurements of Southwest Japan Margin

Data from continuous seismic reflection profiles made across the continental margin on the Philippine Sea side of southwest Japan are used to build on previous studies. The general distribution and trend of various submarine structural units are shown with respect to major tectonic divisions on land. The continental slope has two sections, an upper slope and a lower slope separated by a closely spaced series of sediment-filled basins at intermediate depths. They are parallel to the regional trend of the province and located off large embayments in the coast. The seaward limb of each basin is a sedimentary ridge whose convex side faces the Philippine Sea. At the foot of the lower continental slope is a narrow furrow, called the Nankai trough, which in part may be a developing trench. The intermediate-depth basins, including the outer ridge parts, and the Nankai trough are structurally related units and are analogous to features found west of central Luzon, Philippines.