Aeromagnetic Interpretation of Southwestern Continental Shelf of Korea
Czango Baag, Chang-Eob Baag, 1998. "Aeromagnetic Interpretation of Southwestern Continental Shelf of Korea", Geologic Applications of Gravity and Magnetics: Case Histories, Richard I. Gibson, Patrick S. Millegan
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Analysis of the Project Magnet aeromagnetic data acquired by the U. S. Navy in 1969 permits us to predict a new sedimentary basin, Heuksan Basin, south of the known Gunsan Basin in Block II, offshore South Korea. The basin appears to consist of three subbasins trending north-northwest'south-southeast. The results of our analysis provide not only an independent assessment of the Gunsan Basin, but also new important information on the tectonic origin and mechanism for the two basins as well as for the entire region. The basin-forming tectonic style is interpreted as rhombochasm associated with double-overstepped left-lateral wrench faults. From magnetic evidence, a few northeast-southwest-trending major onshore faults are extended to the study area.
We also interpreted the faults to be left-lateral wrenches. This new gross structural style is consistent with the results of recent Yeongdong Basin analysis (Lee, 1990). The senses of fault movement also are supported by paleomagnetic evidence that the Philippine Sea has experienced an 80 clockwise rotation since the Eocene. Based on a 2.5-D model study, the probable maximum thickness of the sediments in the Gunsan Basin is approximately 7500 m. We believe that the new Heuksan Basin was left unidentified because a high-velocity layer may overlie the basin. Because the overall structural configuration of the Heuksan Basin appears to be favorable for hydrocarbon accumulation, a detailed airborne magnetic survey is recommended in the area, to verify the magnetic expressions of both this thick basin and the tectonic style. A detailed marine gravity survey acquired in conjunction with a highenergy source seismic survey also is recommended, to delineate the sedimentary section and to acquire data supplemental to the magnetics.