A Geophysical Study on the Geotectonics and Opening Mechanism of the Ulleung Basin, East Sea

동해 울릉분지의 지구조 및 성인에 관한 지구물리학적 연구

  • Suh, Man-Cheol (Department of Geoenvironmental Sciences, Kongju National University) ;
  • Lee, Gwang-Hoon (Department of Oceanography, Kunsan National University) ;
  • Shon, Ho-Woong (Department of Geotechnical and Environmental Engineering, Paichai University)
  • 서만철 (공주대학교 지질환경과학과) ;
  • 이광훈 (군산대학교 해양학과) ;
  • 손호웅 (배재대학교 자원환경공학과)
  • Published : 1998.02.28

Abstract

Analysis of gravity, magnetic, and seismic reflection data from the Ulleung Basin, East Sea has provided some insights into the opening mechanism and crustal type of the basin. Free-air gravity anomaly data show positive anomalies of about 40~60 mgal near the Korea Plateau and Oki Bank and of about -20~20 mgal in the central basin. Bouguer gravity anomaly data exhibit NE-SW trending positive anomalies of about 150 mgal in the central basin which is interpreted to be related to high-density crustal material. Abrupt changes in both Free-air and Bouguer gravity anomaly profiles across the basin margins may be due to transition between continental and oceanic crusts. Magnetic anomalies in the basin are generally less than -400 nT. No stripe pattern is evident in the magnetic anomaly map but a NW-SE trending symmetric pattern is seen in some magnetic profiles. The symmetric pattern is probably associated with the high-density crustal material in the central basin suggested by Bouguer gravity anomaly. The acoustic basement in the deep part of the basin has only a small amount of local relief. No graben or half-graben structures are seen in the acoustic basement from which mechanical extension might be inferred. The lack of high-relief structures in the acoustic basement may suggest that the basin is underlain by oceanic crust or that the basement is overlain by thick volcanic layer which obscures the structures and relief of the basement. High-density crust in the central basin inferred from gravity data, abrupt changes in gravity anomalies across the basin margins, symmetric pattern seen in some magnetic anomaly profiles, and lack of relief in the acoustic basement may suggest sea-floor spreading origin of the Ulleung Basin.

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Acknowledgement

Supported by : 한국과학재단