碩士 / 國立臺灣海洋大學 / 應用地球科學研究所 / 100 / Four long-offset reflection profiles (EW9509-3, EW9509-5, EW9509-19, and MCS291-28) and one recently acquired long-offset reflection profile (MGL0908-09) with 5 ocean-bottom seismometers (OBS) that conducted by the project of Taiwan Integrated Geodynamics Research (TAIGER) across the Gagua Ridge in the West Philippine Basin were analyzed in this study. Pre-stack depth migration (PSDM) was implemented to these reflection profiles to image sedimentary structures near the ridge. The velocity-interface result in sedimentary layers from PSDM along profile MGL0908-09 was used as an initial model for OBS data processing, together with previous gravity and OBS studies near the profile. Inversion of refracted, reflected, and head-wave arrivals from OBS data was subsequently applied to build P-wave velocity models from the shallowest layer until the deepest one. Furthermore, integration of previous reflection and refraction result was performed to image sedimentary and crustal thickness around the ridge. Several blind faults can be observed within the lower part of sedimentary in the Huatung Basin, while the faults are less in the West Philippine Basin. West-dipping reflectors within oceanic crust in the West Philippine Basin can be observed from seismic profile EW9509-3 and EW9509-5, which associated with the basement faults and possibly the initial subduction. P-wave velocity-interface model from OBS data shows large lateral variation of velocity of about 4.5-6 km/s and a low velocity of about 4-5 km/s within the upper crust of the Gagua Ridge, which possibly related to fracture zones velocities. Pseudo-3D image of the Gagua Ridge shows that the average sedimentary thickness in the northern part (above 22°N) of the Gagua Ridge is about 2 km for both east and west sides, and thickening up to 8 km beneath the Ryukyu Trench. In the southern part of the ridge (below 22°N), the sediment generally is about 2.5 km thick, and the thickness highly varied due to numerous presences of the basement high and low. Thin sediment (<0.5 km) was found in the west side of the ridge and interpreted as part of the ridge. The crust beneath the ridge thickens northward from 14 km to more than 16 km as observed in the pseudo-3D image of the southern portion of the ridge, and the thickness may reach up to about 20 km in the northern part as the ridge subducted beneath the Ryukyu Trench. The crustal thickness in the Huatung Basin and the West Philippine Basin is about 8-10 km and 6-8 km, respectively, which shows typical thickness for a normal oceanic crust. The Gagua Ridge, interpreted as a set of sub-parallel ridges, resulted from old NE-SW trending fracture zones in the West Philippine Basin that changed orientation into N-S because of anti-clockwise rotation and northwestward convergence of the Philippine Sea Plate.
| Identifer | oai:union.ndltd.org:TW/100NTOU5135013 |
| Date | January 2012 |
| Creators | 王明(Arif Mirza) |
| Contributors | Tan-Kin Wang, 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 | 83 |
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