HR: 0800h
AN: T41E-1257    [Abstracts]
TI: Transition from rifted continental to oceanic crust at the southeastern Korean margin in the East Sea (Japan Sea)
AU: * Cho, H
EM: hmcho@seismic.snu.ac.kr
AF: School of Earth and Environmental Sciences, Seoul National University, Seoul, 151-742 Korea, Republic of
AU: * Cho, H
EM: hmcho@seismic.snu.ac.kr
AF: Marine GeoEnvironment, Korea Ocean Research & Development Institute, Ansan, 426-744 Korea, Republic of
AU: Kim, H
EM: hanjkim@kordi.re.kr
AF: Marine GeoEnvironment, Korea Ocean Research & Development Institute, Ansan, 426-744 Korea, Republic of
AU: Jou, H
EM: htjou@kordi.re.kr
AF: Marine GeoEnvironment, Korea Ocean Research & Development Institute, Ansan, 426-744 Korea, Republic of
AU: Hong, J
EM: jkhong@kopri.re.kr
AF: Polar Applied Science Division, Korea Polar Research Institute, KORDI, Ansan, 426-744 Korea, Republic of
AU: Baag, C
EM: baagce@snu.ac.kr
AF: School of Earth and Environmental Sciences, Seoul National University, Seoul, 151-742 Korea, Republic of
AB: The southeastern Korean margin documents the processes of continental rifting and seafloor spreading that eventually led to the opening of the southern part of the East Sea (Japan Sea). In this study, we present the transitional structure of the southeastern Korean margin and its formation process from rifted continental to 10 km thick normal oceanic crust. The two-dimensional P velocity model of the southeastern Korean margin was computed from ocean bottom seismometer data by tomographic inversion and distilled by iterative forward modeling. The crustal structure shows the emplacement of high-velocity ($>$7 km/s) lower crust under the continental shelf and slope area associated with a rapid transition from rifted continental to oceanic crust. The high-velocity lower crust is interpreted as magmatic underplating formed by voluminous igneous activity during rifting. Magnetic modeling confirms its primary correlation with a prominent magnetic anomaly along the edge of the southeastern Korean Peninsula that is assumed to represent volcanic extrusives and intrusives. The continental margin featuring a rapid transition from continental to oceanic crust exhibits a remarkable decrease in crustal thickness accompanied by shallowing of the Moho over a distance of about 50 km. It thus appears that the Korean margin experienced intense tectonism comprising crustal deformation and volcanism associated with the opening of the East Sea and consequently registered the early history of continental rifting and subsequent sea floor spreading. We suggest that the rifting and subsequent seafloor spreading at the Korean margin was significantly controlled by the supply of magma in a region of hotter than normal mantle temperature.
DE: 7220 Oceanic crust
DE: 8105 Continental margins and sedimentary basins
DE: 6982 Tomography and imaging
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting