本研究使用時序地電阻影像法於臺灣陽明山國家公園小油坑遊憩區進行監測，探討小油坑熱液活動區域之淺部電性構造及其對降雨事件之反應特徵。研究區域位於大屯火山群內，地表可見噴氣孔、泥漿池與氣體逸散等火山熱液活動現象，顯示其地下環境可能受到熱液流體、氣體活動與換質作用影響。此外，研究區域受東北季風及地形效應影響，全年降雨頻繁，天水入滲可改變近地表含水狀態，亦會影響淺部地層之電阻率變化。 本研究於小油坑遊憩區步道兩側布設XP1與XP2兩條時序地電阻測線，使用多波道直流電阻法全自動監測系統輕量版(Remote Resistivity Monitoring System Lite， R2MS Lite)進行監測，每日定時蒐集地電阻資料，並結合降雨資料與現地觀察，探討2024年4月至2025年5月間小油坑之淺部電性構造與降雨反應。本研究除分析研究區域之淺部電性構造、材料分布外，亦依據降雨資料劃分雨場事件，比較不同空間位置於各雨場前後之電阻率變化。 由於不同地質材料之滲透性與水分傳輸條件不同，其降雨反應時間與電阻率變化幅度亦有所差異。本研究透過觀察多場降雨事件前後之最大電阻率降低百分比，辨識主要降雨反應區及優勢入滲位置。研究結果顯示，降雨所造成之電阻率降低反應主要集中於近地表約3公尺以淺區域；於噴氣孔鄰近位置，電阻率降低反應則向較深部延伸，推測與裂隙或破碎構造所形成之優勢水流通道有關。相較之下，泥漿池下方之極低阻區則可能受高度熱液換質且低滲透之黏土化材料影響，其降雨期間之電性反應與一般天水入滲區不同。綜合電性變化與現地觀察，本研究認為降雨入滲可能會改變低滲透黏土化材料周圍之含水狀態、氣體逸散及氣液相比例，間接影響泥漿池與噴泥活動，並據此提出噴泥活動之可能機制。;This study employed time-lapse Electrical Resistivity Tomography (ERT) to investigate the shallow electrical structure and rainfall-induced resistivity responses of the Xiaoyoukeng hydrothermal area in Yangmingshan National Park， Taiwan. The presence of fumaroles， mud pools， gas emissions， and hydrothermally altered materials indicates that the shallow subsurface is influenced by hydrothermal fluids， gas migration， and alteration， while frequent rainfall further modifies near-surface moisture conditions and electrical resistivity. Time-lapse ERT monitoring was conducted along two profiles， XP1 and XP2， installed on opposite sides of the trail， with daily resistivity measurements collected from April 2024 to May 2025. The resistivity data were integrated with rainfall records and field observations to characterize the shallow electrical structure， infer subsurface material distribution， and evaluate spatial resistivity changes associated with individual rainfall events. Rainfall responses varied with material permeability and hydraulic connectivity. Recurrent zones of maximum resistivity reduction were used to identify rainfall-responsive areas and infer preferential infiltration pathways. Most responses were concentrated near the surface， whereas deeper responses near fumaroles suggest fracture-controlled downward water movement. In contrast， the extremely low-resistivity zone beneath the mud pool showed an anomalous response associated with strongly altered， low-permeability clay-rich materials. Together with field observations， the results suggest that rainfall may alter local moisture conditions， gas venting， and gas–liquid distribution， thereby influencing mud-pool and mud-spattering activity and providing the basis for a possible mechanism linking rainfall infiltration to these manifestations.
