Preliminary Study on Seabed Pockmarks in the Hupo Basin of the East Sea (Sea of Japan)

Abstract

The Hupo Basin of the East Sea is located on the eastern continental margin of the Korean Peninsula. KIOST (Korea Institute of Ocean Science & Technology) conducted detailed bathymetry surveys, using multibeam echo-sounders, in the northern part, central part and southern part of the Hupo Basin. The Hupo basin is gradually deepened from the west, coastal area, to the east, deepest to a maximum water depth of about 250 m and bounded by the Hupo bank. The Hupo bank, which is the eastern boundary of the Hupo Basin, has a higher terrain than the surrounding submarine topography. Numerous pockmarks appear at water depths of about 150-200 m in all three areas of the detailed bathymetry surveys. The surface sediments, in the pockmark areas of the Hupo Basin, consist of silt. The sizes of these pockmarks vary widely and are generally about 30 to 50 m in diameter and about 4 to 6 m in depth. The northern part of the three areas has a pockmark density of about 7 per 1 km2. The pockmark densities of the central area and the southern area are about 8 per 1 km2 and about 5 per 1 km2, respectively. The pockmarks are presumed to exist entirely in the Hupo Basin. The pockmarks are supposed to be made by fluid. But we do not know yet whether the fluid is gas or groundwater, and the pockmarks due to other origins. Further studies are needed to clarify the origin of the pockmarks in the future. part, central part and southern part of the Hupo Basin. The Hupo basin is gradually deepened from the west, coastal area, to the east, deepest to a maximum water depth of about 250 m and bounded by the Hupo bank. The Hupo bank, which is the eastern boundary of the Hupo Basin, has a higher terrain than the surrounding submarine topography. Numerous pockmarks appear at water depths of about 150-200 m in all three areas of the detailed bathymetry surveys. The surface sediments, in the pockmark areas of the Hupo Basin, consist of silt. The sizes of these pockmarks vary widely and are generally about 30 to 50 m in diameter and about 4 to 6 m in depth. The northern part of the three areas has a pockmark density of about 7 per 1 km2. The pockmark densities of the central area and the southern area are about 8 per 1 km2 and about 5 per 1 km2, respectively. The pockmarks are presumed to exist entirely in the Hupo Basin. The pockmarks are supposed to be made by fluid. But we do not know yet whether the fluid is gas or groundwater, and the pockmarks due to other origins. Further studies are needed to clarify the origin of the pockmarks in the future.