HR: 0800h
AN: T41B-1306    [Abstracts]
TI: Images of Structural Variation at the Active Collision Boundary of Central Eastern Taiwan
AU: * Kim, K
EM: kwanghee@kordi.re.kr
AF: Korea Ocean Research and Development Institute, B.O.Box 29, Ansan, 425-600 Korea, Republic of
AU: Chiu, J
EM: jchiu@memphis.edu
AF: Center for Earthquake Research and Information, The University of Memphis, Memphis, TN 38152 United States
AU: Pujol, J
EM: jpujol@memphis.edu
AF: Department of Earth Sciences, The University of Memphis, Memphis, TN 38152 United States
AU: Chen, K
EM: chenkc@earth.sinica.edu.tw
AF: Institute of Earth Sciences, Academia Sinica, Taipei, 115 Taiwan
AU: Ma, K
EM: fong@earth.ncu.edu.tw
AF: Graudate Institute of Geophysics, National Central University, Jungli, 300 Taiwan
AU: Yoo, H
EM: hsyoo@kordi.re.kr
AF: Korea Ocean Research and Development Institute, B.O.Box 29, Ansan, 425-600 Korea, Republic of
AU: Min, D
EM: djmin@kordi.re.kr
AF: Korea Ocean Research and Development Institute, B.O.Box 29, Ansan, 425-600 Korea, Republic of
AB: The Longitudinal Valley (LV), located in eastern Taiwan, is considered to be the surface representation of the suture between the Philippine Sea plate (PSP) to the east and the Eurasian continental plate (EUP) to the west. High-resolution 3-D Vp and Vs models are determined in order to understand their relationship with seismicity and tectonic implication. High-quality P and S wave arrival times have been selected from data collected by the Taiwan Seismic Network (TSN) and the Portable Array for Numerical Data Acquisition II (PANDAII) in the Hualien area in central eastern Taiwan. A traveltime tomography package initially developed by Benz (1996) and later modified by Shen (1999) is used in the study. After the determination of reliable 3-D Vp and Vs models, all available earthquakes are relocated to delineate subsurface structures using a recently developed earthquake location program (Chen, 2005). The results of checkerboard resolution tests indicate both P- and S-wave velocity structures can be successfully recovered at least to a depth of 30km for the study area. Thus, significant structures beneath the LV and CR can be reliably recovered by a seismic tomography method under the given station-event configuration. Recovered velocity model along with the relocated earthquake hypocenters clearly depict the deformation structures associated with the active collision. A northwest dipping fault is outlined by the most concentrated seismicity and located at the boundary between the low and high velocity anomaly. A sudden increase in velocity to the east and a sub-vertical extension of the high velocity anomaly (> 6.8km/s) beneath the Longitudinal Valley and Coastal Range suggests that the major faults have juxtaposed different lithologies as a consequence of progressive plate collision. Comparisons among Vp, Vs and Vp/Vs models, relocated seismicity and recent GPS observations indicate the fault defined by planar seismicity may be the major boundary between EUP and PSP, where a significant amount of horizontal crust movement is consumed.
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8015 Local crustal structure
DE: 8103 Continental cratons
DE: 8180 Tomography (6982, 7270)
SC: Tectonophysics [T]
MN: Fall Meeting 2005