.地震前兆观测-地下水水位分析（IV）.PDF

地震前兆觀測－地下水水位分析 (IV) Earthquake Precursor Observation －Analysis of the Ground Water-level Fluctuations (IV) 1 2 1 余貴坤 黃瑞德 甘志文 1.萬能科技大學營建科技學系 2.萬能科技大學通識教育中心 呂佩玲 趙曉玲 中央氣象局地震測報中心 摘 要 分析位於花蓮氣象站的花蓮井地下水位變動與地震的關聯性，顯示花蓮震度 大於等於 2 級時，花蓮井地下水位變動有同震效應出現，經比對 2005 年地震資料， 花蓮井同震水變動約有 120 次，明顯高於以往的研究，最主要的原因在於水位資 料的取樣率不同。前期 2 分鐘取一點，會將大部分的同震水位變動遺漏，近期以 每秒取一點的高取樣率，能適時反應震波傳到水井時的地表震動及岩體變形。除 外，對水位變動極性及變化量，也易誤判 ，造成解釋上的偏差。本研究另分析6 個規模大於 5.0地震的同震水位擾動，顯示水位變動極性與地震錯動的伸張或壓縮 象限一致，若以低取樣率分析，只有 2005/02/18 地震有明顯的同震水位反應，對 中規模地震有如此的影響，小規模地震的同震水位反應更不易觀察。本研究估計 以低取樣率分析時，將遺漏約70~80％同震水位反應。藉由更多資料的分析才能了 解地震能量透過地殼傳輸所產生的同震效應轉換機制。 ABSTRACT In this study, we analyzed the groundwater-level change in the HWA water well for further understanding the relationship between the groundwater-level change and earthquakes. By comparing the groundwater-level change and the occurrences of earthquakes in the Taiwan area during 2005, there are 120 co-seismic perturbations of the groundwater-level due to earthquakes. The number of co-seismic perturbations is obviously higher than those in previous studies. Such difference is mainly from the sampling rate of data. Low sampling rate would result in losing the observations of co-seismic perturbations in the groundwater-level, as in previous studies. We estimated about 70~80% co-seismic perturbations to be lost because of the low sampling rate in data. Six earthquakes with ML≥5.0 are also analyzed for connecting the polarization of 277 the groundwater-level change and the f