HR: 0800h
AN: T51A-0321 INVITED    [Abstracts]
TI: Collision Tectonics of Taiwan and TAIGER Experiments
AU: * Wu, F T
EM: wu@binghamton.edu
AF: Department of Geological Sci. State University of New York at Binghamton, Vestal Parkway East, Binghamton, NY 13902, United States
AU: Lavier, L L
EM: luc@ig.utexas.edu
AF: Institute for Geophysics University of Texas at Austin, J.J. Pickle Research Campus, Bldg. 196; 10100 Burnet Road, Austin, TX 78758- 4445, United States
AU: TAIGER TEAMS, U
AB: By any measure of tectonic activity Taiwan can be described as vigorous. The results from abundant permanent GPS station network on the island show that the convergence of the Philippine Sea and Eurasian plate near Taiwan is about 80 mm/yr and much of the island is sustaining a compressional strain rate in excess of 2 ppm per year in and a dilatational strain of more than 1 ppm per year along the northeastern shore and in a significant portion of the Central Range. Judging from ample thermochronometric data now available on the island it is clear that the rapid uplifting has been ongoing for the last million years. The high seismicity in Taiwan defines parts of the plate tectonic environment and the1999 M7.6 thrust faulting event in central Taiwan and the 2006 M7.1 normal faulting event offshore of Hengchun Peninsula show the variations from subduction to collision from south to north. For longer time scale the Geology of Taiwan shows clearly the accretion of the arc onto the continental shelf. Several tectonic models of Taiwan have been proposed on the basis of available data and tectonic concepts. The implications of these models on the collisional tectonics do not always agree. To resolve them and to build a more comprehensive model of Taiwan detailed information regarding the crust and upper mantle is particularly needed. The TAIGER (TAiwan Integrated GEodynamic Research) program mounts several major field experiments and aims to fill the gap of information. Through active and passive seismic experiments we wish to obtain multi-scale crustal and upper mantle seismic images not only under the island but also around Taiwan for the purpose of defining plate geometry and the configuration of crust and mantle boundaries. The imaging will also target key components in proposed models. For example, the subduction of the Eurasian plate is often included; can we image it as a high velocity anomaly even though it is not seismically active? What is its geometry? At the same time the broadband instruments on land and at ocean floor, mainly to the east and south of Taiwan, will record earthquakes. The passive seismological data will provide a refined map of where the earthquakes, whether interplate or intraplate, are occurring and the plate kinematics. To assess the material properties and the ambient temperature field conductivity profiles from magnetotellurics and laboratory petrophysics have been largely completed. Land broadband seismic stations have been in operation now for six months to more than a year and analysis has begun. A test explosion in Central Taiwan was carried out in October 2006. By early November 2007 broadband OBS deployment should be complete. Three land-based active source profiles and a CDP line across the main boundary between the Foothills and Central Range are scheduled for February/March of 2008. In our preparation to digest this large amount of information and to construct more comprehensive tectonic models we have begun to conduct complete numerical geodynamic experiments, incorporating geometry, ambient conditions, rheological properties of rocks, plate velocities, etc. These experiments, initially only two- dimensional, will allow us to explore the range of initial models that can arrive at an end state that resembles the observations.
DE: 8158 Plate motions: present and recent (3040)
DE: 8168 Stresses: general
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting