HR: 1330h
AN: T12C-0484    [PDF]
TI: Crustal Structure Beneath Taiwan Using Local and Teleseismic Travel Times Observed by the 2001 Linear Array Observation
AU: * Honda, F
EM: fuminori@eri.u-tokyo.ac.jp
AF: ERI,Univ.of Tokyo, 1-1-1 Yayoi,Bunkyo-ku,Tokyo, Tokyo, 113-0032 Japan
AU: Hirata, N
EM: hirata@eri.u-tokyo.ac.jp
AF: ERI,Univ.of Tokyo, 1-1-1 Yayoi,Bunkyo-ku,Tokyo, Tokyo, 113-0032 Japan
AU: Kurashimo, E
EM: ekura@eri.u-tokyo.ac.jp
AF: ERI,Univ.of Tokyo, 1-1-1 Yayoi,Bunkyo-ku,Tokyo, Tokyo, 113-0032 Japan
AU: Sakai, S
EM: coco@eri.u-tokyo.ac.jp
AF: ERI,Univ.of Tokyo, 1-1-1 Yayoi,Bunkyo-ku,Tokyo, Tokyo, 113-0032 Japan
AU: Huang, B
EM: hwbs@earth.sinica.edu.tw
AF: Institute of Earth Sciences Academia Sinica,Taiwan, 128 Academia Road Sec. 2,Nankang Taipei 115 Taiwan, ROC, Taipei, 115 Taiwan
AU: Yen, H
EM: yenhy@earth.sinica.edu.tw
AF: National Central University,Taiwan, Chung-li,Taiwan,32054,R.O.C., Taipei, 32054 Taiwan
AB: In the northeastern area of Taiwan, Philippine Sea Plate is subducting northward, and in the southern area of Taiwan, Eurasian Plate is subducting eastward. These two plates are colliding each other beneath Taiwan. About mountain building mechanism, there are two representative theories, that is, the thin skinned model (Suppe, 1981) and the collision model (Wu et al., 1997). These models have not been resolved yet by well constrained dataset. Based on this background, we deployed a 150-km linear array in central Taiwan from March 2001 to May 2001. The array, which consisted of 55 seismographs spacing at about 2 km, recorded 47 local events that occurred between 23.5\deg\ N and 24.0\deg\ N and 11 teleseismic events. First, we examined teleseismic events to see travel time delays due to lateral heterogeneity in the crust and the uppermost mantle. Delays of the relative travel time of two teleseismic events from Solomon and China reached 1.3 s at the Central Range, which were approximately explained by the preliminary model based on the refraction survey (Yeh et al., 1998). In this model, the shape of the mid-crust is upward convex and the deepest part of the Moho is located east of the Central Range. Next we analyzed crustal structure in detail by using local events. Based on the modified preliminary model which could explain the observations of 5 events located on the array or the extension of the array, we estimated the structure and the hypocenters by using a three-dimensional tomography method (Matsubara, 2001). We modeled the area from 21.0\deg\ N to 26.0\deg\ N in latitude, from 119.0\deg\ E to 124.0\deg\ E in longitude, and from -4.0 km to 72.0 km in depth. The intervals of grids are 1 degree in latitude, 0.2\deg\ (0.1\deg\ from 120.4\deg\ E to 122.2\deg\ E) in longitude, and 4 km in depth. In the checkerboard resolution test, velocities in the crust beneath the array shallower than 20 km were recovered well. The root mean square of travel time residuals, which was 0.66 s for the initial model, was reduced to 0.38 s. The result shows there is a high-speed crust in the eastern coast of Taiwan. We will check if this model can explain the relative travel times of teleseismic events and clarify the structure of the lower crust and the upper mantle
DE: 7218 Lithosphere and upper mantle
DE: 8015 Local crustal structure
SC: Tectonophysics [T]
MN: 2003 Fall Meeting