賈儀平2006-07-252018-06-282006-07-252018-06-282002http://ntur.lib.ntu.edu.tw//handle/246246/118011999 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。 集集地震之後，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。分析濁水溪沖積扇與嘉南平原250 口 以上的觀測井水位資料，初步結果有87 口觀測井產生明顯的地下水位變化。最大 的同震水位變化達1.4 公尺。 主震的水位變化之後的一小時內，規 模4.9(ML)與6.0(ML)的餘震也造成可資辨 別的階狀水位變化。規模6.0 餘震的同震 水位變化有51 口觀測井，其中11 口與主 震同震水位變化反向。規模4.9 餘震的同 震水位變化僅19 口，與主震同震水位變化反向則多達16 口。餘震之同震水位變化與主震反向的現 象在集集地震期間並不常見，原因可能是 觀測井網相對於地震斷層的位置不同：幾 乎所有觀測井都位於車籠埔斷層的下盤， 嘉義地震的盲斷層則位於觀測井網內。 根據相關地震研究，嘉義地震主震的 震源機制為逆斷層，前述兩次餘震的震源機制則以平移斷層為主。從集集地震與嘉 義地震的水位升降分布，再次說明地震斷 層活動產生的大地應變可能是地下水位變 化的主因。Changes of groundwater 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 groundwater level changes, ranging from 1.0 to 11.1m. In the Chianan plain, groundwater level changes were observed 27 wells ranging from 0.1m to 0.9m. On 22 October, an aftershock of ML6.4 occurred near Chia-Yi city. It induced groundwater level changes up to 1.4m in the Choshui River alluvial fan and Chianan plain. Additional changes of water level induced by two aftershocks of ML4.9 and ML6.0 within one hour after the mainshock of Chia-Yi earthquake. During the second aftershock, 51 wells observed water level changes. Of those, the direction of coseismic changes at 11 wells was opposite to that during the mainshock. But during the first aftershock, 19 wells observed water level changes, but 16 coseismic changes behaved oppositely to those during the mainshock. The opposite behavior of water level changes at aftershocks was not apparent during the Chi-Chi earthquake. It might be related to the relative location of the earthquake fault and monitoring wells. While all the wells were located in the footwall of Chelungpu fault, the blind fault of Chia-Yi earthquake should be within the range of monitoring well network. The distribution of water level changes induced by Chi-Chi earthquake and Chia-Yi earthquake indicated the difference of strain field caused by the thrust-fault and strike-slip-fault, and groundwater level is sensitive to the earthquake-induced volumetric strain.application/pdf109981 bytesapplication/pdfzh-TW國立臺灣大學地質科學系暨研究所地下水地震水文地質groundwaterearthquakehydrogeologyreporthttp://ntur.lib.ntu.edu.tw/bitstream/246246/11801/1/902116M002027.pdf