한반도 황해 해역의 지질구조 및 해저지형 특성 연구

Abstract

The Yellow Sea contains subbasins such as the Bohai Bay, West Korea Bay, Gunsan, Heuksan, and Jiangsu basins and is a tectonically crucial area that recorded the Paleozoic-early Mesozoic collision between the Yangtze craton and the Sino-Korean platform. However, the geological structures related to the suture zone between the two crustal blocks have not been reported. In this study, I processed and interpreted the multi-channel air-gun and sparker seismic data acquired from the eastern Yellow Sea off the southern Korean Peninsula for stratigraphic and structural analysis of the area. The interval between the seafloor and the acoustic basement was divided into five seismic units(SU1-SU5) based on the correlation with the IIC-1X well in the Gunsan Basin in the central part of the area. The sparker profiles and multi-beam data were analyzed for seafloor features. The easternmost boundary of the Gunsan Basin is delineated farther eastward from the known boundary by a set of faults, extending from the acoustic basement, that form an arc. In the northern part of the study area, a small graben bounded by normal faults and a half graben-like depression bounded by a strike-slip fault are seen. The acoustic basement in the northern part of the area locally shows synclinal remnants of folded strata which are probably correlated with the Proterozoic Baekryong group found in the Baekryong-do area to the north. Some of the folded strata show evidence of differential erosion on the seafloor which may be equivalent to landforms such as cuesta and mesa. The seafloor above the synclinal remnants is slightly upwarped(relief of about 8 m). The step-like features in the seafloor in the central part of the area are interpreted to be the steeper(about 8°) edges of the tidal ridges formed during the oxygen isotope stage 3(OIS3) (about 50,000 years BP). The folded strata in the acoustic basement and the strike-slip fault in the northern part of the area may be part of the extension of the Qianliyan Uplift in the Shandong Peninsula of China that marks the suture zone between the Yangtze craton and the Sino-Korean platform. The upwarped seafloor above the synclinal remnants further suggests recent or continued but very slow compression or uplift that may have triggered the recent earthquakes in the area.