HR: 1330h
AN: T12A-0443    [PDF]
TI: The Seismic and gravimetric characteristics of the Luzon-Ryukyu Transform Fault, a boundary between the Southeast Asian continental margin and the South China Sea oceanic crust
AU: * Yeh, Y
EM: yeh@oc.gep.ncu.edu.tw
AF: Institute of Geophyiscs, No. 300, Jung-Da Rd., National Central University, Chung-Li, 32054 Taiwan
AU: Hsu, S
EM: hsu@oc.gep.ncu.edu.tw
AF: Institute of Geophyiscs, No. 300, Jung-Da Rd., National Central University, Chung-Li, 32054 Taiwan
AU: Tsai, C
EM: chtsai@oc.gep.ncu.edu.tw
AF: Institute of Geophyiscs, No. 300, Jung-Da Rd., National Central University, Chung-Li, 32054 Taiwan
AB: The northernmost oceanic crust of the South China Sea (SCS) is bounded by the Eurasian continental margin in the northwest, the Taiwan island in the northeast and the Manila Trench in the east. Based on magnetic anomalies, the oceanic crust of the northernmost SCS is terminated by a NW-SE trending transform fault, called the Luzon-Ryukyu Transform Fault (LRTF). The LRTF is supposed to connect the former Ryukyu Trench in the northwest and the former Manila Trench in the southeast. The northwest part of the LRTF is marked by the linear topographic escarpment, along which the Formosa Canyon has developed. Here we use 14 multi-channel seismic reflection profiles to study the crustal structures around the LRTF. To better understand the deep crustal structure, we also perform a gravity modelling to estimate the depth variations of the Moho surface. The results show that in the NW area of the LRTF, the volcanic basement is gradually deeper to the northeast. And, the sediment thickness varies from 1.5~3 twt in the southwest side of the LRTF to 2.5~4 twt in the northeast side. In the SE area of the LRTF, the basement offset of about 1.5 twt is clearly observed. The overlying sediments of about 0.5~1 twt thick have subsided differentially on both sides of the LRTF. Based on calculated bouguer gravity anomaly, a high anomaly (up to 100 mGal ) in this area is observed, which implies a thin crust feature and similar crust characteristics on the both sides of the southern LRTF area. The only obviously fractured volcanic basement, indicating the existence of a transform fault or fracture zone, is observed in the SE end of the LRTF, close to the Manila Trench. The absence of fractured basement along the other part of the LRTF is probably due to the intrusion of the later volcanic activities.
DE: 3010 Gravity
DE: 3025 Marine seismics (0935)
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 3210 Modeling
SC: Tectonophysics [T]
MN: 2003 Fall Meeting