臺灣位在季風氣候影響範圍內，伴隨著季節、地理位置不同，降雨量也隨之變化。為了瞭解臺灣地區近二十年來，地底含水層受到季節性降雨補注所產生的週期性變動，我們藉由CGPS連續觀測資料來分析地表變動與地下水位起伏的關聯性，以用來解釋不同水文地質受到荷重的形態變化。本研究蒐集、分析臺灣高密度Continuous Global Positioning System（簡稱CGPS）資料，獲得每站每日的地表位移坐標，並結合雨量和地下水位資料來探討其特性與意義。從CGPS時間序列進行傅立葉分析可以得顯著的年週期訊號，經由經驗擬合公式獲取其長週期線性趨勢及年週期訊號，得到臺灣地表高程向的垂直振幅，發現最小振幅出現在夏季，最大振幅出現在冬季。
地底含水層形態主要分成兩類：第一類是非受壓含水層，大多分佈在固結岩地區，主要是由岩屑以及靠近地表岩層破裂和風化帶組合而成，在濕季的降雨補注非受壓含水層，使得水位上升、蓄水量增加，然而上覆岩層有效應力往下作用，造成較深處或無地下水的地層壓縮因而地表高程下陷；相反地，在乾季期間地下水位下降、CGPS高程抬升，地下水位與CGPS高程呈現負相關。第二類是於受壓含水層，大多分佈在非固結岩地區，主要是以砂、礫岩組合而成，在濕季的降雨側向補注受壓含水層，使得含水層水壓上升，使得地層膨脹、地表高程呈現抬升；相反地，在乾季期間無補注時呈現下降，是屬於正相關反應。整體主要是以臺灣山區為負相關為主，而平地區則是正相關形態呈現，其中靠近在地下水位敏感補注區的CGPS測站，其相關係數可高達0.82。
除此之外，我們觀測1994年到2016年期間，臺灣長時間的雨量變化與地表垂直變形的關係，藉由計算標準化降雨指標（SPI）來觀測年際間不同程度的乾濕季變化，以及利用CGPS時間序列來推算歷年來的含水層總補注量，發現分別在2002年和2014年期間臺灣有嚴重枯期的現象，因為全區少雨缺水的影響，累積雨量的SPI值接近 -2的情況下，結果明顯反應出山區與平地區皆呈現向上抬升的情況。另外延伸探討西部嚴重超抽地下水而下陷區域，利用CGPS探討不同型態的下陷狀況，以及估算水層參數的可行性。根據我們的結果表示，可以利用CGPS時間序列受到水文負荷和地下結構的影響，並從其特徵和趨勢來明顯分辨不同區域具有不同型態的含水層。

We investigate the relationship between continuous Global Positioning System (CGPS) and seasonal rainfall to understand seasonal-changing surface loading through periodic components in aquifer movement from 1994 to 2016 in the Taiwan region. The main factor controlling the relationship between the CGPS displacement and groundwater level changing in Taiwan is the annual precipitation recharging. We combined observations from 693 rain gauges, 848 groundwater level stations, and 413 CGPS stations to study their relationship. CGPS data were processed by GAMIT/GLOBK to produce daily site positions. We calculated the daily solutions based on a provisional time series model to remove outlier and secular tectonic motion to acquire the annual phase and peak-to-peak amplitude at the CGPS station. Through the Fast Fourier Transform (FFT) analysis, the data presents a yearly sinusoid-like seasonal cycle with a minimum in the summer and a maximum in the winter. We distinguish three different types of pattern based on the Pearson product-moment correlation coefficients between CGPS displacement and the groundwater level changing. For stations near the unconfined aquifers area the correlation coefficient is mainly negative, other areas are mainly positive correlation at confined aquifers area. In particular time series of both CGPS and groundwater level have high correlation coefficients of about 0.82 in the groundwater recharge sensitive areas in both western and southwestern plain, which appears to behave elastically by their high positive correlation coefficients. We also study the past 22 year precipitation-derived standardized precipitation index (SPI) in Taiwan to understand long-term trend changes and we found that Taiwan has been experiencing relatively drought in 2002 and 2014. We found that through CGPS time series by lower-pass filter the plain area of median value up to 15.79 mm and near central mountain range area of median value up to 9.22 mm in recent years. The results show that the patterns of the CGPS time series characteristics and trend are different for different kind of aquifers, and they appeared to be affected by both hydrological loading and sub-surface structure.

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