菁山、竹子湖與擎天崗三口井的地溫變化

本研究為配合經濟部中央地質調查所於大屯火山群區域內菁山、竹子湖以及擎天崗，分別鑽探約200~480 m，直徑約13 cm的三口地熱研究井，放置本所自行研發的新式微小型熱探針串於井內，目的為長期監測大屯火山群地溫，以便未來作為探討大屯火山群火山活動的可能性。菁山測站地下溫度變化，由於岩性以及井內水泥密封工程不完善，20~110 m的深度受到降雨影響較大，最近兩年內的溫度變化幅度約0.446~1.984 ℃；110 m以下溫度變化幅度較小，僅約0.061~0.924 ℃，並且在130 m以下的溫度紀錄有隨時間逐漸下降的趨勢，最近兩年與以前的資料比對亦是如此。竹子湖測站地下溫度變化比菁山測站要來的穩定，在88 m及138 m處的地層疑似連接冷水縫隙，地溫梯度有呈現負值的情形發生，且由於熱量進出必須平衡，因此在88~118 m熱流值(約192.4 mW/m2)有高估的情形。顯示此處熱量往上傳遞的過程中，有大部分都從側向流失。擎天崗測站的監測資料顯示，本測站附近的火山活動確實較為活躍，目前溫度仍在持續上升，上升速度(平均約0.64 ℃/年)及幅度(15個月約0.78 ℃)確實不小，應格外密切觀察其將來之趨勢，不過由於目前之監測時間尚不夠長，因此不敢遽下斷言大屯火山群地底之岩漿已有逐漸上升之趨勢，不過擎天崗地區往上傳遞的熱量流失較少，未來如果有較強烈火山活動發生，勢必會明顯反應在擎天崗測站的溫度紀錄上。

關鍵字

大屯火山群；地溫梯度；熱流值；熱探針；地熱研究井；長期監測

並列摘要

This study was supported by the Central Geological Survey. We analyzed 3 thermal research boreholes at Chinshan, Chuhihu and Chinteinguan located in Tatun volcanic area. The depths of the boreholes are about 200~480 m and the diameters of the holes are around 13 cm. In order to monitor the long-term ground temperature variation of Tatun volcano and to investigate the possibility of volcanism in Tatun volcanic area in the future, we installed a string of the miniature probes in each borehole. As a result of the rock property and the structure of cement between sleeves and rocks at Chinshan station, the down hole temperature variation at the depth of 20~110 m is about 0.446~1.984 ℃ affected by the rain, and below 110 m is about 0.061~0.924 ℃. The temperature below 130 m decreased continuously with respect to time for the previous two years. The temperature at Chuhihu station is relatively stable. As a result of the cool groundwater at 88 m and at 138 m, the temperature gradient is negative. The heat flow is about 192.4 mW/m2 between 88 m and 118 m. We believe that the heat has leaked when passing upward. Chinteinguan is a geothermal active area. The temperature increased continuously for the previous 15 months. The increasing rate(0.64 ℃/year) and amplitude(0.78 ℃/15months) is considerable. Perhaps, it’s too early at this stage to propose that the magma under the Tatun volcanic area is rising, because data recordings are not long enough. We are sure more interesting volcanic signal may come out in the future at Chinteinguan station.

並列關鍵字

Tatun volcano ； borehole temperature ； geothermal gradient ； heat flow ； miniature probe ； long-term monitoring

參考文獻

吳書?? 大屯火山群井下溫度監測研究，國立台灣大學海洋研究所碩士論文，2006。

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Hurwitz, S, Ingebritsen, S.E., and Sorey, M.L., 2002, Episodic thermal perturbations associated with groundwater flow: An example from Kilauea Volcano, Hawaii, J. Geophys. Res., 107, B11, 2297, doi:10.1029/ 2001JB001654.

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Lin, C.H., Konstantunou, K.I., Pu, H.C., Hsu, C.C., Lin, Y.M., You, S.H. and Huang, Y.P., 2005, Preliminary results from seismic monitoring at the Tatun volcanic area of northern Taiwan, Terr. Atmos. Ocean. 16, 3, 563-577.

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菁山、竹子湖與擎天崗三口井的地溫變化

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