| 摘要: | 中新世晚期呂宋島弧斜向碰撞歐亞大陸邊緣，開始台灣造山運動。因此台灣北部地區產生一系列東北西南向的逆衝斷層。隨著造山運動南移的關係，台灣北部從擠壓應力當中釋放，沖繩海槽開始向西擴張，所以台灣北部外海從壓縮應力轉變為拉張應力。前人研究陸上和海上斷層延伸的關係中，顯示基隆外海有存在一條斷層，但此斷層卻沒有往陸上延伸，其原因值得探討。此外，該區域存許多第四紀造山運動後產生的火山群，例如大屯火山群及基隆火山群。火成活動與斷層構造是存在著關係也值得探討。因此，本研究利用多波音束水深、科學測深儀及底質剖面儀三種儀器來探測海床的地形、海床噴氣現象以及海床下的地層構造，藉以了解區域內海床噴氣現象的分布，地形變化以及與活動構造之間的關係。本研究一共使用了17條測線上的魚探儀影像及底質剖面資料，共計76公里。資料來自海洋研究船 OR2 1806、1814、1815、1821 四個航次。研究中利用魚探儀鎖定具有噴氣現象的特定區域，進行地形和底質剖面的特徵探討。研究結果顯示在基隆近海有密集的噴氣現象分布，海床地質成分推測為火成岩性質，顯示這些噴氣現象與自火山活動有關。另外，根據本研究結果判定基隆外海部分沒有由陸地向海域延伸的斷層。Luzon Arc has obliquely collided Eurasian Plate margin since Late Miocene, which has caused Taiwan orogeny, and formed a series of north-east/south-west reverse faults in northern Taiwan. When the orogeny moved southward, the northern part was collapsed after the orogeny, and the Okinawa Trough extends westward. Hence, the stress regime of the northern Taiwan has changed from compression to extension. Between the inland and offshore of Keelung, a fault is suggested in the offshore area but it is not extended to land. Moreover, there’s a group of Quaternary volcanoes, such as Tatun and Keelung volcanic groups. It’s interseting to study the relationship between the volcanism and the structural faults.This study used Multi-beam Echo Sounder, Echo Sounder System, and Sub-bottom Profiler to study the seafloor, plume phenomenon, and the structure of faults beneath the seafloor in northern Taiwan. This study also used data gathered from Echo Sounder System and 17 Sub-bottom Profiler. In total, profiles of 76 kilometers were collected by using the R/V OR2 during the cruises 1806, 1814, 1815 and 1821. In this study, we focus on the area that contains gas plumes, detected by EK60 Echo Sounder. Our results show that there are gas plumes appeared near the Keelung Harbor.The cone-shaped seamount and its associated high density of earthquakes indicate the gas plumes are highly related to the volcanic activity. Finally, we did not observe a structural fault extending from the land to the offshore area of the seamount. |
