HR: 0800h
AN: T11D-1304    [Abstracts]
TI: Paleoseismology of the 1951 earthquake rupture along the Longitudinal Valley Fault at the Guangfu, eastern Taiwan
AU: * Yen, I
EM: yic1228@ms17.hinet.net
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan, Taipei, 106 Taiwan
AU: Chen, W
EM: wenshan@ms.cc.ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan, Taipei, 106 Taiwan
AU: Hwung, N
EM: r86224108@ms86.ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan, Taipei, 106 Taiwan
AU: Yang, C B
EM: d91224003@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan, Taipei, 106 Taiwan
AU: Tsai, K
EM: tkjking@giga.net.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan, Taipei, 106 Taiwan
AU: Chen, Y
EM: geologycyc@yahoo.com.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan, Taipei, 106 Taiwan
AU: Lin, C
EM: lincw@linx.moeacgs.gov.tw
AF: Central Geological Survey, MOEA, No. 2, Lane 109, Hua-Hsin Street, Taipei 235, Taiwan, Taipei, 235 Taiwan
AU: Hou, C
EM: hcs@linx.moeacgs.gov.tw
AF: Central Geological Survey, MOEA, No. 2, Lane 109, Hua-Hsin Street, Taipei 235, Taiwan, Taipei, 235 Taiwan
AU: Liu, Y
EM: jo@crystal.et.ncku.edu.tw
AF: Central Geological Survey, MOEA, No. 2, Lane 109, Hua-Hsin Street, Taipei 235, Taiwan, Taipei, 235 Taiwan
AB: The Longitudinal Valley fault, located at the eastern Longitudinal Valley, has been considered as the collision boundary between the Philippine Sea and Eurasian plates. A series of large earthquakes (M 6.2, M7.0) occurred along the Longitudinal Valley fault, on November 25, 1951. The historical records were documented that the surface rupture extended about 60 km from the Guangfu to Chihshang town, and the surface rupture showed an eastern dipping left-lateral reverse fault with 1.63 m horizontal offset and 1.3 m vertical offset nearby the trench site. We excavated three trenches across a fault scarp in the northern segment near the Guangfu. The excavations show that three bifurcated thrusts dip about 30$\deg$ toward the east. We distinguished three paleoseismic events as the evidence for the occurrence of fault intersected relation and truncation of fault within different stratigraphic units, the younger event break through the ground surface inferred the 1951 earthquake rupture. Based on the stratigraphic dislocation in both sides of the three faults, the vertical offset is 1.0 m, 1.5m and 1.5 m, respectively. By restoring the 1951 earthquake rupture, the major fault still deforms the youngest colluvial deposits (radiocarbon age, B.P. 300). We concluded that at least three paleoseismological events can be identified from those trenches and two events occurred in the past 300 years, and the recurrence interval is less than 250 years.
DE: 7221 Paleoseismology
DE: 8107 Continental neotectonics
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting