大屯火山群位於台灣北部，根據分析噴氣之氦同位素顯示，部分噴氣來自岩漿源，說明台灣北部地下有岩漿庫存在之可能，從地震分佈與震源特性，亦顯示七星山及大油坑附近有明顯的微震活動存在，初步推斷此地區之微震可能是岩層裂縫中液態或氣態物質之震動所造成，這些現象與國外其他火山地區所觀測之岩漿相關活動類似，再由電性構造亦顯示，七星山及大油坑附近之上部地殼中所觀測到電性地層分佈，在地下約6 Km深處，發現一近似球狀構造，可能與岩漿庫有關(圖1)，再從台灣北部因碰撞作用所生成的造山崩解張裂活動亦逐步加強發育當中，張裂活動隨時有可能提供充分管道給岩漿噴發至地表，因此大屯火山地區進一步仔細探查，確認岩漿庫存在之真實性有其必要。本研究計畫將於七星山地區建立大地電磁法監測站兩座，主要目的在監測孔隙中之流體之相變化(沸騰汽體亦或凝結流體)所引起之電阻變化以及地熱生產所引起之電阻變化，此監測可以提供母岩與流體交互作用之演化過程極具價值之訊息，以瞭解是否岩漿庫存在之可能及其活動。工作項目主要包括測站選定、監測站建立、分析電性構造，配合地質資料、地溫資料、微震觀測及地表地殼變形等資料上約制，以建構完整的大屯山地區火山岩漿存在及活動範圍。 The Tatun volcano group is located at the northern tip of Taiwan. Based on the geochemical analysis from fumarole gas shows that the Helium isotope ratios are very high and strongly indicate that some magma chambers might still exist beneath the Tatun volcano group area. The seismic array recorded several volcanoseismic signals, that have often been reported in active volcanoes worldwide. In addition, the resistivity section also indicated a dome structure at depth around 6 km that is closely related to the structure of magma chamber (Figure 1). Combining the earthquake activity and the resistivity section along with the previous analysis of Helium isotope ratios, we suggest that it should be further investigated whether the magmatic plumbing system beneath the Tatun volcano group is still working. It is thus proposed to establish two magnetotelluric (MT) observation sites at locations around the TUK (大油坑) crater, because MT impedance is stable and has high temporal resolution. The monitoring of electrical resistivity structure and continuous MT measurements will show promise in terms of imaging subsurface magma, because magma (melt) and degassed volatiles (if mixed with groundwater) are highly conductive, especially with the repeated electrical measurements will be revealing a high precision of resistivity and its changes. By correlation with the other geophysical and geology data, the possible movement of subsurface magma will be inferred during the MT monitoring. 研究期間：10008 ~ 10107
