독도화산체 정상부의 지구물리학적 특성 연구

Abstract

Multi-beam, magnetic, sub-bottom profiling, and side scan sonar survey data for the eastern part of the summit area of the Dokdo volcano obtained in 1999, 2004, 2007 were analyzed to investigate the geophysical characteristics of the summit of the Dokdo. The Dokdo volcano is located in the northeastern part of the Ulleung Basin in the East Sea (Japan Sea) and composed of very small islets and a large submerged volcanic edifice. There are two voluminous seamounts (the Simheungtaek and the Isabu Tablemounts) at the east side of the Dokdo. They have submerged guyot summits, occurring at depths of about -200 meters. Bathymetry and topographic data around the Dokdo show uneven seabed and irregular undulations from costal line to -100 m in water depth, indicating the effects of partial erosions and taluses. The stepped slope in the topographic profile is supposed to be a coastal terrace suggesting repetition of transgressions and regressions in the Quaternary. The bathymetry and the side scan sonar data show a small crater, assumed to be formed by the eruption of later volcanism, at depth of -120 m in the northeastern part of the survey area. The sub-bottom profiles and the side scan sonar images propose that, except some areas with shallow sand sedimentary deposits, there are rocky seafloor and lack of sediments in the survey area, dominantly. The rocky seabottom elongated northeastward from the islets of the Dokdo might be the residual part of the eroded and collapsed crater of the Dokdo volcano. The results of the magnetic anomaly, the analytic signal, and the magnetization inversion have a good coherence with above other consequences regarding to the location ofthe residual crater.