HR: 1340h
AN: T43B-1340    [Abstracts]
TI: Folding and Faulting at Tanliwun Along Leading Edge 1999 Chi-Chi Thrust
AU: Johnson, A M
EM: gotesson@purdue.edu
AF: Department of Earth and Atmospheric Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907, United States
AU: * Huang, W
EM: huang22@indiana.edu
AF: Department of Earth and Atmospheric Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907, United States
AU: * Huang, W
EM: huang22@indiana.edu
AF: Department of Geology Sciences, Indiana University, 1001 East 10th Street, Bloomington, IN 47405, United States
AU: Chen, W
EM: wenshan@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No.1, Roosevelt Rd., Sec. 4, Taipei, Taipei, 106, Taiwan
AU: Chen, Y
EM: seilee@eq.ccu.edu.tw
AF: Deparment of Earth and Enviromental Sciences, National Chung-Cheng University, 168, University Rd., Min-Hsiung, Chiayi, 621, Taiwan
AU: Lu, S
EM: ding@moeacgs.gov.tw
AF: Central Geological Survey, MOEA, 2, Lane 109, Hua-Hsin Street, Chung-Ho, Taipei, 235, Taiwan
AB: The 1999 Chi–Chi earthquake in Taiwan provided excellent opportunities for studying earthquake faulting and folding in escarpments 1 to 10 m high at the leading edge of the Chi-Chi thrust which extended for some 100 km. Trenches excavated across the escarpments showed well–preserved fault and fold structures at scales ranging from mm to m. We studied in detail relations between profile shapes of escarpments and subsurface structures exposed in Chushan trench at Tanliwun, near the south end of Chi–Chi rupture. We mapped faults and sedimentary bedding at scales of 1:10 or 1:20 in the trench walls. In order to understand the structures exposed in the trench walls, we supplemented the observational approach with theoretical modeling. For example, we used multi–fault dislocation modeling to show that the multiple small faults exposed in the trench walls could have produced the monocline–like escarpments observed there. The field observations and the modeling suggest that the structures that first appeared to be continuous monoclinal bending of layers are, in fact, discontinuous. The appearance of gross bending is a result of slip in the same sense along numerous small faults inclined to the sedimentary bedding and subparallel to the main fault in the near subsurface.
DE: 8004 Dynamics and mechanics of faulting (8118)
DE: 8005 Folds and folding
DE: 8012 High strain deformation zones
SC: Tectonophysics [T]
MN: 2007 Fall Meeting