碩士 / 國立臺灣海洋大學 / 地球科學研究所 / 107 / In this study, ocean-bottom seismometer (OBS) and multi-channel seismic (MCS) data across the middle Taiwan Strait were analyzed along the southeastern profile of HX05 with 10 Taiwan OBSs shot from GI guns and a northwestern profile of HX05 with 2 Fujian OBSs shot from an air-gun array in June 2017. By using the refracted and reflected arrivals from OBS data, we inverted the P-wave velocities and interfaces layer by layer to obtain the sedimentary model along profile HX05. Furthermore, we integrated the MCS data along 8 profiles to build a pseudo-3D model near HX05. We also analyzed two horizontal components of OBS data to build a Poisson’s ratio model along profile HX05. In the P-wave velocity-interface model along profile HX05, we found a gap of 0.8 km height at the basement due to the normal faulting formed by Littoral Fault Zone between Wuchiu Depression and Penghu Platform in the southeast. A low-velocity zone or a fracture zone, caused by the faults across the basement and the upper crust, was also imaged between Wuchiu Depression and Kinmen Rise in the northwest. The normal faulting caused by Littoral Fault Zone in the southeast is more active than that in northwest. Thus, the Wuchiu Depression features a tilted half-graben, similar to Nanjihtau Basin and Penghu Basin nearby. Furthermore, along profile HX05, we found relatively low Poisson's ratios in sedimentary layers below the Penghu Platform affected by the normal faults owing to the soft sediment. No horst appears below the shallow seafloor so that not the structural uplift but the sands and muds carried by currents from Penghu Channel formed the shallow seafloor of the West Changyun Ridge. The pinch-out structures of the sedimentary layers is probably the end of the deposition of West Changyun Ridge. On the other hand, based on the pseudo-3D model near HX05, the depth of the basement gradually becomes shallow from the southeast to the northwest. In the middle Taiwan Strait and Kinmen Rise, the sediment was eroded and the pinch-out structures was caused by lifting of the forebulge. The forebulge was formed between 12.5 Ma and 4 Ma owing to Philippine Sea Plate over-thrusting the ancient South China Sea Crust. The formation of the forbulge in the second stage was after 4 Ma due to the Taiwan orogenic belt. The loading of the Taiwan orogenic belt and westward movement caused the migration of the forebulge. We suggest that the top of the current forebulge is located on the Penghu platform or west of the Wuhu platform. Although HX05 profile is situated at the forebulge in the foreland basin system, we still found several local depressions in the Penghu Platform near the footwall of the boundary fault at Penghu Basin and the normal fault in the Taishi Basin. On the other hand, a wide range of the shallow basement was imaged at the hanging wall of the boundary fault at Nanjihtau Basin.
| Identifer | oai:union.ndltd.org:TW/107NTOU5135002 |
| Date | January 2019 |
| Creators | Wei, Ren-Jie, 魏仁潔 |
| Contributors | Wang, Tian-Kai, 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 | 72 |
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