| Summary: | 碩士 === 國立臺灣海洋大學 === 應用地球科學研究所 === 97 === An experiment of Continental Shelf Survey Program (CSSP), by using 14 micro-OBSs onboard Military Ship TA-KUAN and 24-channel reflection seismic onR/V Ocean Researcher I, was conducted offshore SE Taiwan in September 2006. The aim of this paper is to explore the crustal structures paralleled to the Gagua Ridge in the Huatung Basin and the Eastern Trough of Gagua Ridge. Two initial models from MCS data were built first, refracted and reflected travel times of OBS data then are used to invert two P-wave velocity models. Imaging of velocity models along Huatung Basin and Eastern Trough of Gagua Ridge shows rugged basements. Sedimentary thickness east and west of Gagua Ridge in OBS models increase northward from about 1.7 km to 3 km and southward from about 1 km to 3.8 km, respectively. Similarly, crustal thickening northward from about 7 km to 10 km is observed from the P-wave velocity model east of Gagua Ridge whereas crustal thickening southward from about 7 km to 11 km is found west of Gagua Ridge. The crustal thickening northward along the Eastern Trough of Gagua Ridge have resulted from the northwestward convergence of Philippine Sea Plate. However, based on the OBS modeling, the crustal thickening southward west of the Gagua Ridge supports the transpression that may have also generated left-lateral strike-slip faults and fracture zones in both sides of the Gagua Ridge.
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