賈儀平2006-07-252018-06-282006-07-252018-06-282001http://ntur.lib.ntu.edu.tw//handle/246246/117721999 年9 月21 日集集附近發生規模 7.3(ML)的強震，導致西南部平原地下水觀 測網之地下水位產生異常變化。其中以鄰 近車籠埔斷層的濁水溪沖積扇最為顯著， 有157 口觀測井產生明顯的地下水位變 化，其中67 口觀測井的水位變化超過1 公尺，最大變化達11.1 公尺。其次是嘉南 平原，有52 口觀測井產生明顯的地下水位 變化，有27 口觀測井的水位變化超過0.1 公尺，最大變化達0.9 公尺。 以數位記錄與類比記錄綜合分析比對 九二一地震前後濁水溪沖積扇之水位異常 變化，在地震發生時，每小時一筆的數位 記錄顯示地下水位呈階梯式升降；而連續 性的類比記錄則可觀測到水位振盪與階梯 式升降。同震的水位變化並不限於受壓含 水層，部份受壓和自由含水層也有明顯反 應。地下水位的回復需時數分鐘到數月以 上不等，視水文地質條件而定。濁水溪沖 積扇之觀測井距離車籠埔斷層2 至50 公里 不等，同震水位變化與距離斷層遠近相 關，推測與車籠埔斷層錯動產生的應變場 使絕大部份下盤地區受到壓縮，但在鄰近 斷層的地區則出現伸張的現象。 集集大地震之後，緊接著在10 月22 日於嘉義市西北方發生規模6.4(ML)的地 震。嘉義地震並未在地表產生明顯之錯 動，鄰近震央的濁水溪沖積扇與嘉南平原 部份觀測井亦產生地下水位異常變化，變 化幅度可達0.4 公尺。此次地震造成之水 位升降，在部份井站與集集地震產生的水 位異常變化反向，推測是不同的斷層活動 之大地應變機制不同造成。Changes of ground water levels induced by the ML7.3 Chi-Chi earthquake on September 21, 1999 were recorded at 157 monitoring wells in the Choshui River alluvial fan. Of those, 67 observed large ground water level changes, ranging from 1.0 to 11.1m. These Wells are clustered at 64 stations located approximately 2 to 50 km form the north-south trending Chelungpu fault. Generally step-like changes of water level were observed at the time of earthquake on the hourly digital records, while both oscillatory and step-like changes were observed on the analog records. Co-seismic changes of ground water level were recorded not only in the confined aquifer but also in the partially confined aquifer and the unconfined aquifer. The recovery of water level changes in an aquifer took minutes to months, depending primarily on hydrogeologic conditions of the confining layers. The sign of co-seismic water level change at a well varied with its distance from the fault. The strain field inferred from the co-seismic water-level changes due to the Chi-Chi earthquake suggests that volumetric contraction predominated in most of the footwall area; whereas volumetric expansion prevailed in a belted area adjacent to the fault zone. On 22 October, another earthquake of ML6.4 occurred near Chi-yi city. It induced the groundwater level changes at some monitoring wells in the Choshui River alluvial fan and Chinan plain, up to 0.4m. The scattering of groundwater level changes, revealed the complexity of geologic structures of Chi-yi region.application/pdf28964 bytesapplication/pdfzh-TW國立臺灣大學地質科學系暨研究所地震地下水水文地質earthquakegroundwaterhydrogeologyreporthttp://ntur.lib.ntu.edu.tw/bitstream/246246/11772/1/892116M002050.pdf