HR: 1340h
AN: T43B-1343    [Abstracts]
TI: Neo-tectonic pattern of the southwestern tip of the Okinawa Trough backarc basin (Ilan Plain, Taiwan)
AU: * Ku, C
EM: 93642003@cc.ncu.edu.tw
AF: Institute of Geophysics, National Central University, Taiwan, No.300, Jhongda Rd., Jhongli City, 320, Taiwan
AU: Hsu, S
EM: hsu@ncu.edu.tw
AF: Institute of Geophysics, National Central University, Taiwan, No.300, Jhongda Rd., Jhongli City, 320, Taiwan
AU: Sibuet, J
EM: jcsibuet@ifremer.fr
AF: Institute of Applied Geosciences, National Taiwan Ocean University, No.2,Pei-Ning Rd., Keelung, 202, Taiwan
AB: The Ilan Plain is located at the southwestern tip of the Okinawa Trough backarc basin which propagates westward into the Taiwan orogen. On May 15, 2002 and two times on March 5, 2005, three large earthquakes occurred in the near of the coastline of the Ilan Plain. To understand the relationship between the earthquake mechanisms and the geological context, we have collected seven seismic reflection profiles roughly parallel to the coastline of the Ilan Plain. A major normal fault, trending approximately ENE-WSW has been identified east of the locations of the two earthquakes of March 5, 2005, in the prolongation of the ENE-WSW trend of their aftershock seismicity. This feature has been named the Ilan Shelf Fault and might extend to the east along the northern trend of the Ilan continental spur. The centroid seismic moment tensor solutions of the March 5, 2005 earthquakes are both of left-lateral strike-slip faulting type and are consistent with GPS data, showing that the Ilan Shelf Fault is a normal fault with a left-lateral strike-slip component. Based on GPS data, we suggest that a pseudo-rigid block, limited in the west by the Lishan Fault and in the north by the Ilan Shelf Fault, has rotated clockwise due to the northwestward collision of the Luzon Arc with Taiwan. The clockwise block rotation is the mechanism causing the left-lateral strike-slip motion along the Ilan Shelf Fault. The Ilan Shelf Fault is a major tectonic and structural feature which corresponds to the southern boundary of the tip of the Okinawa Trough backarc basin.
DE: 1029 Composition of aerosols and dust particles
DE: 3001 Back-arc basin processes
DE: 3025 Marine seismics (0935, 7294)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting