碩士 / 國立臺灣海洋大學 / 應用地球科學研究所 / 104 / Gagua Ridge, the largest linear ridge in the western part of the Philippine Sea Plate off eastern Taiwan, is northward subducted beneath the Eurasian Plate in the Ryukyu subduction zone. In this study, we analyzed 14 four-component ocean-bottom seismometer (OBS) data along MGL0906-16 (T4) line of the 2009 TAIGER experiment to build a P-wave velocity model and a Poisson’s ratio model across the northern Luzon Arc, the Huatung Basin, the Taitung Canyon, the northern Gagua Ridge and the West Philippine Basin off eastern Taiwan. Firstly, P-wave velocities and interfaces of the sedimentary layers were built by considering a pre-stack depth-migrated (PSDM) model analyzed from the long-offset reflection data. Secondly, the refracted and reflected arrivals, propagating through the crustal structures, picked from OBS data layer by layer were used to invert the P-wave velocities and interfaces of the crustal model, respectively. Models of P-wave velocities and interfaces enabled us not only to build initial models of Poisson’s ratio but also to set up the converted interfaces (such as basement, intra-crust and Moho interfaces) for shear-wave modeling. Finally, we identified the phases of the converted shear waves and picked their travel-times from two horizontal components of OBS data to invert the Poisson’s ratio model. Based on the crustal models, crustal thickness below the Huatung Basin (about 9.5 km) is thicker than that below the West Philippine Basin (about 8 km) due to northwestward compression of the Philippine Sea Plate. The low P-wave velocity zone (4.0-4.7 km/s) in the Gagua Ridge may be owing to deformation, fractures or faults. On the other hand, caused by magma intrusion of igneous rocks are found in the middle and lower crust below the Huatung Basin as shown by a high P-wave velocity zone (about 7.5-7.9km/s) and relatively low Poisson’s ratio (0.243-0.255). Based on the map of the sedimentary and crustal thickness, crustal thickness is northward increased (about 16 km) since Philippine Sea Plate is subducted beneath Eurasia Plate. Furthermore, the crustal thickness below the Gagua Ridge is thicker (15-17 km) than two sides of it, and the Gagua Ridge is northward subducted beneath Philippine Sea Plate. The fracture zones, parallel the Gagua Ridge, are observed at top and both sides of the Gagua Ridge by transpression. We also observed caused by magma intrusion of igneous rocks below the Huatung Basin. Therefore, we suggested that the Gagua Ridge might be formed by initial subduction.
| Identifer | oai:union.ndltd.org:TW/104NTOU5135006 |
| Date | January 2015 |
| Creators | Deng, Yi-Jie, 鄧以傑 |
| Contributors | Wang, Tan-Kin, 王天楷 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 62 |
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