HR: 1330h
AN: T12C-0477    [PDF]
TI: Crustal Deformation of a Transition Zone Between Collision and Subduction: GPS Measurements in Southwestern Taiwan
AU: * Hu, J
EM: jchu@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 106 Taiwan
AU: Shen, L
EM: li3s5@ms9.hinet.net
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 106 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
AU: Chan, Y
EM: yuchang@earth.sinica.edu.tw
AF: Institute of Earth Sciences, Academia Sinica, No. 128, Sec. 2 Academia Road, Taipei, 115 Taiwan
AU: Rau, R
EM: raurj@mail.ncku.edu.tw
AF: Deaprtment of Earth Sciences, National Cheng Kung University, No.1, Ta-Hsueh Road,, Tainan, 701 Taiwan
AU: Lai, T
EM: tim@linx.moeacgs.gov.tw
AF: Central Geological Survey, MOEA, No. 2. Lane 109, Hua-Hsin Street,, Taipei, 235 Taiwan
AB: Five to six years of GPS measurements have been carried out by Central Geologic Survey since 1996 in southwestern Taiwan. The Pingtung-Kaohsiung network consists of 43 stations for investigating the crustal deformation and the land subsidence. We used Bernese software to calculate the station velocity of above-mentioned GPS stations by using the three measurements form August 1996 to August 1999. These GPS surveys have provided the complete velocity field relative to the Paisha station (S01R) of the Penghu islands, which is considered as the stable continent shelf. We also calculated the principal strain rate, shear strain rate, rotation rate and dilatation rate by using QOCA software developed by JPL. GPS displacement velocities display the trends of variation in the investigated area. The station velocities are 42.2 mm/yr to 55.5 mm/yr in the azimuth from 245.4$\deg$ to 272.5$\deg$. Station velocities decrease westwards and nearly increase southwards. In terms of velocity vector trends, there is a contrast in kinematics in study area. In the central and western part of the study area, GPS stations move nearly toward the west, whereas in the Kaohsiung and Pingtung coastal area, the displacement vectors demonstrate a clear counter-clockwise deviation toward SW. Our results clearly demonstrate that the tectonic escape may occur in southwestern Taiwan during the oblique collision. Chaochou fault is the major fault in studied area is considered as the thrust fault with left-lateral movement. Based on our studies, the velocity gradients of the GPS stations across the Chaochou fault are not significant. This implies that the Chaochou fault is locked and the mechanical coupling along the fault plane should be very strong. Furthermore, we divided the studied area into 15 subnets for strain rate calculation. The strain analysis demonstrate that the average maximum and minimum strain rate is 0.21$\pm$0.02 $\mu$strain/yr and -0.46$\pm$0.02 $\mu$strain/yr, respectively. The maximum compression axe is 99.7$\pm$1.2$\deg$ in average. The maximum strain rate is 1.08$\pm$0.02 $\mu$strain/yr in the azimuth 27.49$\pm$3.6$\deg$. The minimum strain rate is -1.26$\pm$0.17 $\mu$strain/yr in the azimuth 120.9$\pm$3.1$\deg$. The strain rates in 4 subnets near Chaochou fault demonstrated significant transtensional deformation.
DE: 1206 Crustal movements--interplate (8155)
DE: 8107 Continental neotectonics
SC: Tectonophysics [T]
MN: 2003 Fall Meeting