HR: 14:25h
AN: T33E-04    [Abstracts]
TI: Lithospheric Deformation of a Young Arc-continent Collision Orogen: GPS Observations in South Taiwan
AU: * Ching, K
EM: kuenmiao@yahoo.com.tw
AF: Department of Earth Sciences, National Cheng Kung University, No.1, Ta-Hsueh Rd, 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 Rd, Tainan, 701 Taiwan
AU: Hou, C
EM: hcs@moeacgs.gov.tw
AF: Central Geological Survey, MOEA, 2, Lane 109, Hua-Hsin Street, Chung-Ho, Taipei, 235 Taiwan
AB: Oblique collision often generates transpressional deformation and lateral extrusion with difference degree of coherence between crust and upper mantle. In the early stage of oblique collision, however, relationship between surface deformation and deep-seated motion remains an enigma. GPS data collected from a densely-spaced network of 120 survey-mode GPS stations in south Taiwan, deployed by Central Geological Survey of Taiwan between 1995 and 2004, provide a great opportunity to comprehend the mode of lithospheric deformation in the young Taiwan orogeny. South Taiwan is divided into, from west to east, coastal plain, alluvial fan and metamorphic belt, divided separately, by a NE-SW trending Chishan fault and a N-S trending Chaochou fault, respectively. We estimated south Taiwan station velocities relative to a stable Chinese continental margin station. Each station has two to nine measurements. The resulted GPS velocity field indicates a homogeneous counterclockwise rotation with velocities of 54.98 ± 11.25 mm/yr from 292° to 248° across south Taiwan, except for the area west of Chishan fault. For the stations west of Chishan fault, station velocities decrease westwards from 50.2 mm/yr to 9.8 mm/yr along azimuths from 260° to 240°. Based on the strain rate field derived from the velocity field, most areas in south Taiwan show minor dilatation rate and shear strain rate. However, large strain rates are presented in several regions. Predominant NW-SE shortening and NE-SW lengthening are illustrated in the area west of Chishan fault and part of the region east of southern Chishan fault segment. In addition, maximum shear strain rates exist along the Chishan fault. Obvious NE-SW extension and NE-SW shear strain are shown in the southernmost coastal area of Pintung alluvial plain. Part of areas along the Chaochou fault and southernmost portion of Taiwan display noticeable E-W extension and nearly N-S shear strain. By combining surface velocities, shear wave splitting data and bathymetry south of Taiwan, our tectonic model for south Taiwan indicates that surface deformation is coupled with upper mantle flow and most surface faults are locked in south Taiwan. Predominant flow may mainly distribute on the ductile shear zone beneath Chaochou fault, and subduction suction along Manila trench in SW Taiwan may be another driven force to generate block rotation in south Taiwan. In addition, southern segment of Chishan fault is an apparent discontinuous structure in southern Taiwan, which reflects movement of detachment in the upper curst.
DE: 1209 Tectonic deformation (6924)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 8011 Kinematics of crustal and mantle deformation
DE: 8012 High strain deformation zones
SC: Tectonophysics [T]
MN: Fall Meeting 2005