HR: 1340h
AN: T43B-1338    [Abstracts]
TI: The transition zone between two structural domains in the active fold-and-thrust belt of central Taiwan.
AU: * Huang, C
EM: chunghuang@ntu.edu.tw
AF: Institute of Earth Sciences, Academia Sinica, 128 Academia Road Sec. 2, Nankang, Taipei, 115, Taiwan
AU: * Huang, C
EM: chunghuang@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 106, Taiwan
AU: Chan, Y
AF: Institute of Earth Sciences, Academia Sinica, 128 Academia Road Sec. 2, Nankang, Taipei, 115, Taiwan
AU: Hu, J
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 106, Taiwan
AU: Yang, K
AF: Exploration and Development Research Institute, CPC Corporation, No. 1, Dayuan, Wenfa Road., Miaoli City, 360, Taiwan
AU: Huang, S
AF: Exploration and Development Research Institute, CPC Corporation, No. 1, Dayuan, Wenfa Road., Miaoli City, 360, Taiwan
AU: Lee, J
AF: Institute of Earth Sciences, Academia Sinica, 128 Academia Road Sec. 2, Nankang, Taipei, 115, Taiwan
AB: The structural transition zones within fold-and-thrust belts usually contain complex structures and are often controlled by the basement geometry. In the western foothills of central Taiwan, most of the transition zones coincide with the high-angle normal faults within the basement, and these faults significantly influence the transitional structures. In this study, we focus on the northern Taichung basin, which is a transition zone between two structural domains in central Taiwan. They are folds-dominated domain in Miaoli and imbricate thrusts- dominated domain in Taichung. Series of large earthquakes occurred in 1935 in the Miaoli domain, and the devastating Chi-Chi earthquake occurred in 1999 in the Taichung domain, indicating the transition zone is possibly a highly active area. A 3-D geological model was established based on seven published balanced cross sections plus one cross section constructed in this study. The constructed cross section is based on the surface geological data and relocated earthquake hypocenters. The 3-D geological model indicated that the transition zone was initially developed as a north-south trending fold. The fold was then truncated by a south-dipping normal fault, which also separates the two structural domains at depth. The southern part of the truncated fold further acted as the footwall for a newly developed fault-bend fold, which is located underneath the Chi-Chi earthquake fault. The fault-bend fold structure may constrain the NW movement of hanging wall and cause large uplift for the northern section of the Chi-Chi earthquake fault. In addition, the surface trace of the Chi-Chi earthquake fault changed from the N-S direction to the E-W direction due to the geometric constraints of the fold.
DE: 8000 STRUCTURAL GEOLOGY
DE: 8005 Folds and folding
DE: 8010 Fractures and faults
SC: Tectonophysics [T]
MN: 2007 Fall Meeting