HR: 14:15h
AN: T13F-03    [Abstracts]
TI: Seismogenic structure of the 1935 Hsinchu-Taichung (MGR=7.1) earthquake, Miaoli, western Taiwan
AU: * Lin, Y N
EM: r92224104@ntu.edu.tw
AF: Institute of Geosciences, NTU, No. 1, Sec. 4, Roosevelt Rd., Taipei, 106 Taiwan
AU: Chen, Y
EM: ygchen@ntu.edu.tw
AF: Institute of Geosciences, NTU, No. 1, Sec. 4, Roosevelt Rd., Taipei, 106 Taiwan
AU: Wu, Y
EM: drymwu@ntu.edu.tw
AF: Institute of Geosciences, NTU, No. 1, Sec. 4, Roosevelt Rd., Taipei, 106 Taiwan
AU: Yang, K
EM: 155055@cpc.com.tw
AF: Exploration and Development Res. Inst., CPC, Dayuan No. 1, Wenfa Rd., Miaoli, 360 Taiwan
AU: Yoko, O
EM: ota@iceice.com
AF: Yokohama National University, Minamisenzoku, Otaku, Tokyo, 2-11-13-20 Japan
AB: A large earthquake (M$_{GR}$ 7.1) took place in Miaoli on April 21, 1935 and caused severe damage in surrounding area. The associated surface ruptures daylighted the Tuntzuchiao Fault (TTCF), trending NE between the Tachia and Taan River, and the Chihhu Fault (CHF), a separate back thrust trending N-S in the Shihtan area, which is 30 km north from the TTCF. In this study, we try to clarify the structural geometry and further identify the seismogenic structure for this event. The fold-and-thrust belt in Miaoli region is characterized by three major styles of structural interactions of thrusts and folds: the reactivated pre-existing normal faults, the low angle thrust cutting through the shallow strata, and the regional d\'{e}collement at the base of the sedimentary strata in depth. The hypocenter of the 1935 mainshock is located right beneath the middle reach of the Taan River. By subsurface geology, we consider that the reactivation of the pre-existing normal fault preserved in the footwall of the Sanyi Fault may be the seismogenic structure of this earthquake. It currently performs strike-slip in character and extends to the ground surface as the TTCF in the south. Combining the surface rupture and geologic map data, we interpret the CHF as a back thrust located in between two E-W strike-slip faults at both northern and southern ends. With this clear boundary condition, we incorporate the coseismic and interseismic triangulation data and remodel the fault plane geometry of both CHF and TTCF. Despite the two recorded surface ruptures, topography shows no strong evidence to infer a long development history. Therefore we conclude the two faults are either new or with relatively long recurrence interval.
UR: http://active.gl.ntu.edu.tw/People/index.htm
DE: 8000 STRUCTURAL GEOLOGY (New field, replaces single entry 8165)
DE: 8015 Local crustal structure
DE: 8102 Continental contractional orogenic belts
DE: 8107 Continental neotectonics
DE: 8123 Dynamics, seismotectonics
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting