HR: 17:15h
AN: T54A-06    [Abstracts]
TI: Crust and Upper Mantle Structural Models Associated with the Active Subduction and Collision Tectonics in the Taiwan Region from 3-D Tomographic Inversion and Earthquake Relocations
AU: * Chiu, J
EM: jerchiu@memphis.edu
AF: CERI, the University of Memphis, 3904 Central Ave., Memphis, TN 38152 United States
AU: Kim, K
EM: kwangheekim@gmail.com
AF: KORDI, Ansan P.O. Box 29, Seoul, 425-600 Korea, Republic of
AU: Pujol, J
EM: jpujol@memphis.edu
AF: Dept. of Earth Sciences, the University of Memphis, Johnson Hall, Memphis, TN 38152 United States
AU: Chen, K
EM: chenkc@earth.sinica.edu.tw
AF: Institute of Earth Sciences, Academia Sinica, P.O. Box 1-55, Nankang, Taipei, 115 Taiwan
AU: Huang, B
EM: hwbs@earth.sinica.edu.tw
AF: Institute of Earth Sciences, Academia Sinica, P.O. Box 1-55, Nankang, Taipei, 115 Taiwan
AU: Yeh, Y
EM: yehyh@earth.sinica.edu.tw
AF: Institute of Earth Sciences, Academia Sinica, P.O. Box 1-55, Nankang, Taipei, 115 Taiwan
AB: 3-D Vp and Vs models for the crust and upper mantle beneath the Taiwan area have been determined using selected high-resolution earthquake data from an island-wide seismic network and two local seismic arrays. All earthquakes in the Taiwan CWB catalogue are then relocated using the resultant 3-D Vp and Vs models. The depth of the Moho varies significantly, especially along the E-W direction. In the western Coastal Plain and Western Foothills the depth of the Moho is around 35 km, which deepens gradually eastward, reaches a maximum depth of ~55 km beneath the eastern Central Mountain Range, shallows up rapidly beneath the Longitudinal Valley and Coastal Range, and merges with the thin Philippine Sea Plate offshore of eastern Taiwan. In central Taiwan, the Central Mountain Range (CMR) is bounded to the east and west by two steeply westward dipping active faults from the upper crust to a depth of about 30 km. Therefore, the uplifted and thickened CMR serves as a backstop for the converging Eurasian and Philippine Sea plates. The crust beneath the CMR is characterized by a brittle, high-velocity and seismically active upper crust (<15 km) and a ductile, low-velocity and aseismic mid-to-lower crust (below 15 km), most probably due to the high geothermal activity from the excess heat supplied from the hot upper mantle beneath the thin oceanic crust to the east, from the surrounding hotter upper mantle beneath the thickened continental crust, and from shear heating during active collision. The collision zone in eastern Taiwan is characterized by an active and steeply eastward dipping seismic zone along a region of low Vp and high Vp/Vs ratio near the Taitung region in SE Taiwan. It transforms into an active westward steeply dipping seismic zone along a transition zone between the high Vp and Vs oceanic crust and the low Vp and Vs continental crust near Hualien region in central eastern Taiwan. The geometry of the subduction zone in northeastern Taiwan can be clearly imaged from the relocated earthquake locations. Behind the subduction, a region of low Vp and high Vp/Vs ratio at depths of 5 to 10 km can be identified beneath the Tatun-Chilung volcano group indicating a potential magma reservoir. Two steeply dipping linear seismic zones in the volcano region may mark the upward escape paths of the magmatic materials in the region.
DE: 7218 Lithosphere (1236)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7270 Tomography (6982, 8180)
DE: 8150 Plate boundary: general (3040)
SC: Tectonophysics [T]
MN: Fall Meeting 2005