利用GPS連續站監測九芎坑斷層活動特性

A Study on the Characteristics and Regional Signals for Chiuchiungkeng Fault with Continuous GPS Statons

台灣主要的地震多發生於西部地區造山前緣附近，本研究選定台灣西部雲林至台南造山帶前緣地區的九芎坑斷層進行全球定位系統（GPS）的連續觀測分析，以便了解此地區地表活動的行為，所得之結果可作為未來此地區大地基準更新或維護的參考。為了連續監測九芎坑斷層的活動，了解其地表變化量，中正大學地環系架設了10個全球定位系統之CGPS站（Continuous GPS stations, CGPS stations），配合經濟部中央地質調所的7個CGPS站，共同構成一個地區性的GPS監測網，研究使用的是Bermese V.5.0來解算各CGPS站之坐標解，以便於觀察九芎坑斷層在地表的變化量，及斷層活動特性與地區性訊號，研究的時間段為2007年9月1日至2010年12月31日，共1218天。本CGPS監測網在每年5月至10月間，CGPS站的坐標每日解有明顯離散的現象（大約為± 2 cm），與台灣梅雨和颱風季節的時段相符，在以FFT檢驗後，發現三條基線的最顯著信號之頻率為一年一次，符合台灣的乾濕季。為了確定離散顯著的時段是由乾濕季的因素所影響，因此使用每日雨量資料加以比對，發現一年最大的降雨量都落在離散之時段，大約為7到9月，且頻譜的結果與乾濕季吻合。GPS觀測所得的斷層壓縮量介於3.61 ± 0.48到6.15 ±0.68 mm之間，由北向南遞增，斷層整體是在被擠壓的狀況，並且發現在斷層的北端有右移的量（0.99 ± 0.31 mm），最後測試模擬出九芎坑斷層面的可行性。 Major earthquakes generally occurred in western Taiwan. This study uses Continuous GlobalPositioning System (CGPS) stations from Yulin to Tainan. In order to continuously monitor theactivities of Chiuchiungkeng fault, 10 CGPS stations established by the Department of Earth andEnvironmental Science, National Chung Cheng University. In addition 7 other CGPS stations from the Central Geological Surrvey were also included in this study. Bernese v.5.0 GPS was used to solvefor the coordinates of the CGPS stations. The time span of study period is 2007/9/1 - 2010/12/31, atotal of 1218 days. It is found that a relative larger deviation, about ± 2 cm , in the daily coordinatesbetween May to October in each year, which corresponds well with the rainy season and thethyphoon season in Taiwan. In the FFT test we found the most significant signal of frequency is oncea year, is match with wet and dry season in Taiwan. With correspondence to the official rainfallrecord, it is found that the most deviation in the daily GPS solution occurred at the days close to theoccurrence of the maximum rainfall each year. The fault is being compressed between 3.61 ± 0.48and 6.15 ± 0.68, increase from north to south, and found the northen end of the fault has shifted toright lateral (0.99 ± 0.31 mm). Finally we tested the feasibility of simulating the fault plane ofChiuchiungkeng fault.

Major earthquakes generally occurred in western Taiwan. This study uses Continuous GlobalPositioning System (CGPS) stations from Yulin to Tainan. In order to continuously monitor theactivities of Chiuchiungkeng fault, 10 CGPS stations established by the Department of Earth andEnvironmental Science, National Chung Cheng University. In addition 7 other CGPS stations from the Central Geological Surrvey were also included in this study. Bernese v.5.0 GPS was used to solvefor the coordinates of the CGPS stations. The time span of study period is 2007/9/1 - 2010/12/31, atotal of 1218 days. It is found that a relative larger deviation, about ± 2 cm , in the daily coordinatesbetween May to October in each year, which corresponds well with the rainy season and thethyphoon season in Taiwan. In the FFT test we found the most significant signal of frequency is oncea year, is match with wet and dry season in Taiwan. With correspondence to the official rainfallrecord, it is found that the most deviation in the daily GPS solution occurred at the days close to theoccurrence of the maximum rainfall each year. The fault is being compressed between 3.61 ± 0.48and 6.15 ± 0.68, increase from north to south, and found the northen end of the fault has shifted toright lateral (0.99 ± 0.31 mm). Finally we tested the feasibility of simulating the fault plane ofChiuchiungkeng fault.