HR: 11:25h
AN: T11F-05    [PDF]
TI: 3-D kinematics analysis of surface ruptures on an active creeping fault at Chihshang, Eastern Taiwan
AU: * Lee, J
EM: jclee@earth.sinica.edu.tw
AF: Inst. Earth Sciences, Academia Sinica, P.O. Box 1-55 Nankang, Taipei, 115 Taiwan
AU: Angelier, J
EM: jacques.angelier@lgs.jussieu.fr
AF: Univ. Paris 6, Dept. G‚otectonique, Paris, 75005 France
AU: Chen, H
EM: hychen@earth.sinica.edu.tw
AF: Inst. Earth Sciences, Academia Sinica, P.O. Box 1-55 Nankang, Taipei, 115 Taiwan
AU: Chu, H
EM: chuht@linx.moeacgs.gov.tw
AF: Central Geological Survey, P.O Box 968 Chungho, Taipei, 220 Taiwan
AU: Hu, J
EM: jchu@ccms.ntu.edu.tw
AF: National Taiwan University, Dept Geosciences, Taipei, 104 Taiwan
AB: The Chihshang fault is one of the most active segments of the Longitudinal Valley Fault, the plate suture between the converging Philippine and Eurasian plates. A destructive earthquake of M 7.1 with substantial surface scarps resulted from rupturing of the Chihshang fault in 1951. From that on, no big earthquake greater than M 5.5 occurred in this area. Instead, the Chihshang fault reveals a creeping behavior at a rapid rate of about 20 mm/yr at least during the past 20 years. The surface breaks of the creeping Chihshang fault can be observed at the several places. A typical feature is reverse-fault-like fractures on the retaining wall. We deployed small geodetic networks across the fault zone at five sites. Each network comprises of 5 to 15 benchmarks. Trilateration measurements including angles and distances as well as leveling among the benchmarks have been carried out on an annual basis or twice a year since 1998. Compared to previous other measurements which have shown the first order creep rate for the entire fault zone, the present geodetic data provides the detailed information of the surface movements across the fault zone which usually composed of more than one fault strands and folds structures. According to our data from the local geodetic networks, we are able to reconstruct the 3-D kinematics of surface deformation across the Chihshang fault zone. Multiple fault strands are common along the Chihshang fault. Oblique shortening occurred at all sites and was characterized by a combination of thrusts, backthrust and surface warps. Strike-slip motion can also be distinguished on some fault strands. It is worth to note that the cultural feature, such as concrete basement of strong resistance, sometimes acted as deflection of surface ruptures. It should be taken into consideration for mitigation against seismic hazards.
DE: 1206 Crustal movements--interplate (8155)
DE: 7223 Seismic hazard assessment and prediction
DE: 8102 Continental contractional orogenic belts
DE: 8107 Continental neotectonics
DE: 8150 Plate boundary--general (3040)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting