台灣位於歐亞板塊與菲律賓海板塊的碰撞交接帶，活躍的地體構造使台灣地區有相當多的斷層分布。由於台灣北部人口密集，且鄰近核能發電廠，如果近海地震或火山活動可能產生災害性海嘯。因此本研究使用一般海洋地球物理資料來探討野柳舺與基隆嶼間近海的海床構造與噴氣現象。 本研究採用海研二號1806、1814、1821、2120等四個航次的水深、科學漁探儀、底質剖面和側掃聲納的資料，研究測線總長約138公里。台灣東北部近海存有許多正斷層並呈現半地塹之樣貌，本研究結果發現緊鄰野柳岬東側有一條東北-西南向線性陷落構造，推測該構造是正斷層，延該斷層有多出海床逸氣現象，其南端可能接近崁腳斷層，因此推測可能是陸上崁腳斷層的延伸。另外，在野柳舺與基隆嶼間的海底地形有錐狀地形構造，由於其下方是高磁化基盤，且有許多小地震伴隨，推測該海底錐狀體是海底火山遺留的火山頸，錐狀突起構造周圍的海床有許多噴氣現象集中，根據氣體採樣分析判斷推測噴氣來源含深部岩漿之氣體。另外有些海床噴氣位置呈現東北-西南走向，判斷與台灣東北部外海區域構造背景呈現張裂狀態有關，並藉由地殼弱帶向上噴發。 ;Taiwan is located in a collision zone between the Eurasian Plate and the Philippine Sea Plate. There are lots of structural faults due to the active tectonics around Taiwan. There is a big population in northern Taiwan. Besides, there are two nuclear power plants at the coast of northern Taiwan. If there is near-shore earthquake or volcanic activity, a tsunami may be generated and cause serious damage. For that, based on marine geophysical data, this study is aimed to understand the near-shore geological structure and the seabed gas emission phenomenon between the Yehliu cape and the Keelung islet. In this study, we use the multi-beam data, EK echo sounder, sub-bottom profiler and side-scan data collected during the R/V OR2 cruises 1806, 1814, 1821 and 2120. The total length of the ship track is about 138 km. Structurally, there are several normal faults or half-grabens in the offshore area of northern Taiwan. Our results show that there is a NE-SW trending linear structure located immediately in the east side of the Yehliu cape. We interpret the structure as a normal fault. Along the linear structure, seabed gas emissions can be observed. Because the souther end of the structure is very close to the Kenchiao Fault in northern Taiwan, we suggest that the structural fault is the offshore prolongation of the Kenchiao Fault. Moreover, there is a cone-shaped seafloor morphology located between the Yehliu cape and the Keelung islet. Because the area is located in a relatively high magnetization zone and there are lots of small earthquakes beneath the bathymetric structure, we interpret the cone-shaped structure as a relic volcanic neck. Around the volcanic neck, there are lots of seabed gas emissions. The collected gas indicates that its source could be from deep magma. Some other locations of seabed gas emissions follow the trend of NE-SW direction and could be related to the general trend of the northern Taiwan mountain belt. The “gases” could migrate upward along the existing faults or fractures.
