비정상적 심해성 연해해분에 관한 연구

A study on the subducting deep marginal basin

One One remarkable correlation has been noticed with a number of marginal basins are being subducted by itself. For example, extinct Philippine Sea basins are subducted. the West Philippine Basin at the Philippine and Ryukyu Trenches, the Shikoku and Parece Vela Basins at the Nankai Trough. Similar cases are observed in the Woodlark Basin subducting northeastward at the Solomon Trench, the South China with the Manila Trench. the South Fiji Basin with two subduction zones: the Hunter subduction zone in the northwestern end of the basin. and the Kadavu subduction zone in the northeastern end of the basin and the Solomon Basin with three subduction zones, the New Britain, the Bougai nville, and the Trobriand Trenches. All these basins are several hundreds meters deeper than the normal oceans. The Sulu and Celebes Basins have traces of past subduction. These basins are also deeper than the normal oceans by about 600 m and 950 m. respectively. Among them fully subducting basins such as the Philippine Sea and Solomon Basin seem to be deeper than partially subducted basins such as the South Fiji and South China Basins. In sharp contrast several marginal basins with depths close to those of the normal oceans are not being subducted at their margin. High density of upper asthenosphere beneath deep back-arc basins is likely to be a necessary condition for occurrence of subduction in such small marginal basins.