Crustal analysis of the Ulleung Basin in the East Sea (Japan Sea) from enhanced gravity mapping
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ORIGINAL PAPER
Crustal analysis of the Ulleung Basin in the East Sea (Japan Sea) from enhanced gravity mapping Chan Hong Park Æ Jeong Woo Kim Æ Nobuhiro Isezaki Æ Daniel R. Roman Æ Ralph R. B. von Frese
Received: 8 September 2005 / Accepted: 28 July 2006 / Published online: 21 October 2006 Springer Science+Business Media B.V. 2006
Abstract To facilitate geological analyses of the Ulleung Basin in the East Sea (Japan Sea) between Korea and Japan, shipborne and satellite altimetryderived gravity data are combined to derive a regionally coherent anomaly field. The 2-min gridded satellite altimetry-based gravity predicted by Sandwell and Smith [Sandwell DT, Smith WHF (1997) J Geophys Res 102(B5):10,039–10,054] are used for making cross-over adjustments that reduce the errors between track segments and at the cross-over points of shipborne gravity profiles. Relative to the regionally more homogeneous satellite gravity anomalies, the longer wavelength components of the shipborne anomalies are significantly improved with minimal distortion of their shorter wavelength components. The resulting free-air gravity anomaly map yields a more coherent integration of short and long wavelength anomalies
C. H. Park Marine Environment Department, Korea Ocean Research & Development Institute, Ansan 426-744, Korea J. W. Kim (&) Department of Geoinformation Engineering, Sejong University, Seoul 143-747, Korea e-mail: [email protected] N. Isezaki Department of Geology, Chiba University, Chiba 260, Japan D. R. Roman National Geodetic Survey, NOAA, Silver Spring, MD 20910, USA R. R. B. von Frese Department of Geological Sciences, The Ohio State University, Columbus, OH 43210, USA
compared to that obtained from either the shipborne or satellite data sets separately. The derived free-air anomalies range over about 140 mGals or more in amplitude and regionally correspond with bathymetric undulations in the Ulleung Basin. The gravity lows and highs along the basin’s margin indicate the transition from continental to oceanic crust. However, in the northeastern and central Ulleung Basin, the negative regional correlation between the central gravity high and bathymetric low suggests the presence of shallow denser mantle beneath thinned oceanic crust. A series of gravity highs mark seamounts or volcanic terranes from the Korean Plateau to Oki Island. Gravity modeling suggests underplating by mafic igneous rocks of the northwestern margin of the Ulleung Basin and the transition between continental and oceanic crust. The crust of the central Ulleung Basin is about a 14–15 km thick with a 4–5 km thick sediment cover. It may also include a relatively weakly developed buried fossil spreading ridge with approximately 2 km of relief. Keywords Shipborne and satellite gravity Æ Cross-over adjustment Æ Ulleung Basin Æ Gravity modeling Æ Transitional crust Æ Fossil ridge
Introduction The crustal properties of the Ulleung Basin (Fig. 1) are important to establish when exploring Korea’s offshore energy and mineral resources (Park 1990, 1998), and for im
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