許多大地震發生之前，都可以偵測到地磁與重力的改變。當岩層受到應力作用，因岩石脹容(rock dilatancy)現象會造成地表變形；另外，應力作用也可能使岩層有質量轉移(mass transfer)的現象，這些現象都會造成地表重力值的改變。九二一大地震後，經檢視全省磁力連續觀測資料發現，位於車籠埔斷層兩端的磁力站—鯉魚潭站及灣丘站，都觀測到磁力異常訊號，這些異常訊號與地震的發生有時間上的巧合。本計畫將分重力及磁力兩部份進行。重力方面，根據文獻記載，在規模較大的地震發生前，震央附近重力基點的重力值有變化的情形，可作為地震前兆現象研究項目之一；本計畫選擇橫跨觸口斷層的重力基點進行重複觀測，以監測該斷層活動所衍生的重力變化。磁力方面，將藉由全省地磁連續觀測網資料，分析磁力變化與地震發生的關聯性。 Local changes in gravity and geomagnetic field can be expected before lots of large earthquakes occur. Changes in elevation for the rock dilatancy and the redistribution of crust mass due to the tectonic stresses can cause gravitational variation. Also, many examples of gravity changes accompanying both seismic and aseismic deformations have been reported. After Chi-Chi earthquake, numerous magnetic anomaly signals were observed in the northern and southern parts of the Chelungpu fault, and it is coincided with the time of Chi-Chi earthquake occurred. In this project, the repeated microgravity survey along the profile across the Chukou fault is one of the items included in the earthquake precursor research program to detect the gravity variation across known active faults. Furthermore, in magnetism study, the relationship between magnetic anomaly and earthquake will be analyzed by using the data from eleven continuous geomagnetic stations in Taiwan. 研究期間：9901 ~ 9912
