在天然氣水合物賦存的海域，甲烷與硫化氫等氣體可能從沉積物深部藉由斷層或其他通道往海床上冒出，天然氣往海床的上沖或噴出經常伴隨地質構造形成各式樣貌如泥貫入體、泥火山或麻坑等，因此瞭解海床地貌聲納影像及海床下淺層沉積物的構造和特徵是了解海床下流體及天然氣水合物形成極重要的研究項目。傳統上海洋地球物理調查如震測、磁測等是將探測儀器放在近海水面附近作遙測式的量測，但是複反射、氣泡或船體噪音很容易會影響到收集資料的品質。底拖式的儀器有效減少許多不必要的訊號干擾並且接近待探測物體可以及有效提高訊號強度，因此本計畫主要目的在於使用底拖側掃聲納系統(包含側掃聲納、底質聲納剖面儀及磁力儀)，以貼近海床的方式進行資料蒐集，作為台灣西南海域天然氣水合物的精密調查工作，進而提升對海床淺層地質特性的解析調查能力。此外，由於台灣西南海域大致缺乏精密多頻道(多音束)水深資料，所以本計畫另一重要工作項目是進行多音束水深量測，描繪台灣西南海域天然氣水合物賦存區的精密海底地形測量和分析。此計畫的另一項重要工作是做為發展底拖式海底地電磁探測工作的先期工作，藉著連繫合作暸解國外在海底地電量測和應用在天然氣水合物調查的情形，以進一步提升精密調查我國天然氣水合物的狀態和分布的能力。 ; In gas hydrate resources areas, fluid such as methane or sulfide may come to the sea floor through sediment layers by means of faults or other venting passages. The upward flow of fluid may form distinctive features such as mud diapir, mud volcanoes or pockmarks. Therefore, understanding the morphological characteristics of the sea floor through acoustic images of deposited or structural characteristics of shallow sediment layers is important to study the mechanism of sediment fluid flow and gas hydrate formation. Traditionally, marine geophysical surveys usually put the instruments near the sea surface; however, multiple reflection, bubble effect or noise from the survey vessel generally influences the data quality. Deep-towed instruments on the other hand can mitigate noise and increase signal amplitude. The main task of this project is to use a deep-towed side-scan sonar system (including side-scan sonar, sub-bottom profiler and magnetometer) to collect and analyze data close to the seafloor, in order to have a detailed mapping of the gas hydrate bearing areas off SW Taiwan. Because in the area off southwest Taiwan the multibeam bathymetric data are usually missing, we will collect multibeam bathymetric data to map the seafloor characteristics of the gas-hydrate formation areas. Another task of this project is to understand the deep-towed controlled source EM methods and expect to introduce such kind of marine EM surveys in the offshore area of SW Taiwan. ; 研究期間 9702 ~ 9712
