HR: 0800h
AN: T51A-0311    [Abstracts]
TI: Dimensionality Analysis and Geo-Electric Structure of Long-period Magnetotelluric Data, Southern Taiwan, TAIGER project
AU: * Chiang, C
EM: 93642006@cc.ncu.edu.tw
AU: Chen, C
EM: chusen@earth.ncu.edu.tw
AU: Bertrand, E A
EM: bertrand@phys.ualberta.ca
AU: Unsworth, M J
EM: unsworth@phys.ualberta.ca
AU: Turkoglu, E
EM: eturk@phys.ualberta.ca
AU: Hsu, H
EM: 946202013@cc.ncu.edu.tw
AU: Hill, G
EM: gjhill77@gmail.com
AB: The Taiwan orogen has formed as a result of the arc-continent collision between the Eurasian continental margin and the Luzon island arc over the last 3 million years. It is the type example of an arc-continent collision. In 2004, the Taiwan Integrated Geodynamical Research (TAIGER) project was formed and began a systematic investigation of the crustal and upper mantle structure beneath Taiwan. This included new magnetotelluric (MT) data collection to study the geo-electrical structure beneath Taiwan. High quality long period MT data has been collected through collaboration between National Central University, Taiwan, and the University of Alberta, Canada. In total, 82 long-period MT stations were deployed on 4 cross- island profiles in Taiwan with a remote reference station located on Penghu Island in the Taiwan Strait. The remote reference is ~50km from the main island of Taiwan and is used to reduce cultural noise effects in these data from the populated mainland. Dimensionality analysis from tensor decomposition has been performed on these data using the McNeice-Jones algorithm. The results of this analysis indicate that the electrical structures are two-dimensional with dominant strike directions N45° E, N37° E and N29 ° E in northern, central and southern Taiwan, respectively. As expected, these strike directions are essentially parallel to the regional geology. The decomposition parameters of shear, twist and anisotropy for these profiles are small, indicating the 2-D strike directions are well constrained. The dimensionality analysis presented implies that the generation of 2- D inversion models will be appropriate for these data. The results of 2-D inversion show that the collision boundary between the Eurasian and Philippine Sea Plates is beneath the central range in the southern profile. A low resistivity zone is located beneath the western foothills. At mid-crustal depth, a boundary is imaged between conductive western sedimentary rocks and the resistive metamorphic rocks to the east which form the main orogenic belts of the central ranges. This margin occurs near the trace of the Cauchow fault where there is evidence of a conductor rising to the surface. This conductor may be related to interconnected fluids and/or thermal effects in the mid crust. In this paper, the analysis of these data will be examined in detail and the tectonic implications discussed.
DE: 1744 Tectonophysics
DE: 8038 Regional crustal structure
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 9320 Asia
DE: 9605 Neogene
SC: Tectonophysics [T]
MN: 2007 Fall Meeting