HR: 10:55h
AN: T11F-03    [PDF]
TI: Present-day Crustal Deformation Across Central-Western Taiwan Fold-and-Thrust Belt From GPS Observations, 1996-1999
AU: * Ching, K
EM: jing_kuen@sinamail.com
AF: Department of Earth Sciences, National Cheng Kung University, No.1, Ta-Hsueh Road, Tainan, 701 Taiwan
AU: Rau, R
EM: raurj@mail.ncku.edu.tw
AF: Department of Earth Sciences, National Cheng Kung University, No.1, Ta-Hsueh Road, Tainan, 701 Taiwan
AU: Hou, C
EM: hcs@linx.moeacgs.gov.tw
AF: Central Geological Survey, MOEA, No.2. Lane 109, Hua-Hsin Street, Chung-Ho, Taipei, 235 Taiwan
AB: Development of arcuate fold-and-thrust belt in central-western Taiwan is controlled by salients in the portions of the foreland basin. Published GPS data in central-western Taiwan are too sparse to clarify the present-day crustal deformation of individual geological structures in this region. An 80-km aperture GPS network with 5-km station-spacing has been deployed by Central Geological Survey of Taiwan since 1996. Here we use GPS campaign data from 1996 to 1999 to estimate the velocity field and strain rate variations in this region. GPS velocity field with respect to a stable continental margin site (Penghu) suggests a gradual increase in motion from west (2.0-7.7 mm/yr) to east (11.9-18.6 mm/yr) in central-western Taiwan. Except in southwest coastal area, site velocities increase abruptly from west (6.3 mm/yr, $32\deg$) to east (10.7 mm/yr, $349\deg$). This velocity boundary which extends 20 km long in N$10\deg$E direction is located just 5 km east of the coast. Such a contrast in velocity field creates a notable principal shortening rate 1.2 $\mu$strain/yr $120\deg$ across this boundary. Farther to the east, block motions of Pakua anticline which located between Changhua Fault and Chelungpu Fault are moving 4.9-6.3 mm/yr in NW direction relative to the west of the Changhua Fault. The principal strain rates at Pakua anticline are 0.3 $\mu$strain/yr $13\deg$, and -0.3 $\mu$strain/yr $103\deg$. East of Pakua anticline, the shortening rate of Chelungpu Fault is 6.0 mm/yr in $320\deg$ relative to the west of Pakua anticline. The dramatic change of GPS velocity field in southwest coastal area suggests the existence of a low-angle blind fault. Growth of this fault is likely resulted from westward propagation of Taiwan deformation front. Variations of velocity field across Changhua Fault indicate a left-lateral motion, which may be caused by localized wrench deformation along the northern edge of Peikang high. By using a simple elastic dislocation model, GPS observations will be used to estimate the slip rates of each fault in this area.
DE: 1206 Crustal movements--interplate (8155)
DE: 1744 Tectonophysics
DE: 8015 Local crustal structure
SC: Tectonophysics [T]
MN: 2003 Fall Meeting