台灣西南海域位於增積岩體（accretionary wedge）與南中國海北側大陸邊緣斜向聚合 的區域。增積岩體上有一系列線性排列的褶皺與逆衝斷層地形。大陸邊緣則主要由一系列 張裂盆地上覆厚層沉積物組成。本研究區域座落於增積岩體下部斜坡中的好景海脊（Good Weather Ridge）北端。根據地物、地化與地熱的研究，西南海域蘊含著豐富的天然氣水合 物(gas hydrate)。此外，全世界至少一半以上的油氣田，在地表面或海床都有油氣的徵兆， 而含有天然氣水合物的區域，也多半可在海床面上找到相關徵兆。因此，本研究利用高解 析側掃聲納(side-scan sonar)與底質剖面儀(sub-bottom profiler)來調查此區海床面以及淺層 地層中天然氣水合物的相關特徵，並進一步與深部構造進行連結，以建立研究區域內天然 氣與天然氣水合物的賦存模型。 我們收集了13 條的底拖側掃聲納與底質剖面資料，其結果顯示研究區域內分布大量 侵蝕構造且形貌上有所不同。根據資料結果我們也將過去震測資料所解釋的幾條逆衝斷層 位置進行修正。此外，在研究區域中我們發現麻坑構造、泥火山、自生碳酸鹽以及聲波透 明帶等天然氣水合物相關的特徵，這些特徵的存在代表研究區域內天然氣供應充足，且有 良好的移棲通道。由於研究區內有大量海底仿擬反射（Bottom Simulating Reflectors）存在， 且溫壓條件適合天然氣水合物形成，因此我們推測位於麻坑構造附近之聲波透明層內，很 可能含有固態的天然氣水合物。綜合所有資料的分析與比對結果，我們建立了研究區域內 天然氣移棲與天然氣水合物賦存的三維模型。The offshore area of the SW Taiwan is located in the oblique convergence zone between the northern continental margin of South China Sea and accretionary wedge. In the accretionary wedge, there are a series of folds and thrust faults. The continental margin consists of a series of the rifted basin and thick sediments. Our study area is located in the northern Good Weather Ridge of the lower slope of the wedge. According to the geophysical, geochemical and geothermal researches off SW Taiwan, abundant gas hydrate may exist. Our main purpose is to use high-resolution sidescan sonar and sub-bottom profiler to survey the near seafloor features of the gas hydrate formation off SW Taiwan. We have collected 13 deep-towed lines in northern Good Weather Ridge. The results show that many erosion features are found in study area and their morphology are different. Besides, we modify some thrust faults location on the basic of our results. We also find pockmarks, mud volcano, authogenic carbonate and acoustic transparent zones. These features imply that there are abundant gas and fluid paths in this region. Our study area is suitable for forming gas hydrate in terms of temperature and pressure condition. These evidences indicate that there is high potential for preserving gas and gas hydrate in our study area. Therefore, we suggest that the material in acoustic transparent layers which are near the pockmarks may be gas hydrate. After integrating all data, we construct a 3D model for the gas migration and gas hydrate-bearing in our study area.
