印度板塊對歐亞板塊的碰撞擠壓而導致青藏高原隆升是全球近代極為重要的地質事件，現今大地測量觀測與地質記錄一致反映，青藏高原構造演化除了擠壓抬升外，同時還有伸張構造，在藏南地區發育出一系列的南北向正斷層及地塹。亞東-谷露裂谷帶是西藏規模最大的一條近南北向裂谷帶，大致沿90oE展佈，起於尼泊爾喜馬拉雅，橫穿雅魯藏布縫合線，向北沿念青唐古拉山延伸，全長超過500 km，是西藏規模最大的一條近南北向裂谷帶，亞東-谷露裂谷及其附近地區的地震活動性頻繁頻繁。本研究針對2008年10月6日，西藏自治區當雄縣規模6.3的地震做同震形變及震後形變的分析及探討。 目前的青藏地區監測方法主要有光學遙感圖像、地面調查核對等，但這些方法對於大面積無人區、全天候無障礙監測很難完成，而合成孔徑雷達干涉測量 (Synthetic Aperture Radar Interferometry, InSAR)是近幾年興起的一門用於形變監測的技術，作為一種全天候、大範圍、高精度、可不受氣候與日夜影響拍攝、可以從空間進行長期連續監測的對地觀測技術，可彌補這些方法的不足。 本文採用ALOS衛星PALSAR傳感器，其為L波段，因為長波長的特性，有較好的相干性(Coherence)，適合於地形較複雜區域監測。同震形變以採用合成孔徑雷達差分乾涉 (DInSAR)技術獲取地表變化的相位信息，結果顯示，當雄地震位於羊易盆地的次級斷層上，最大下陷量於震央區高達30公分；利用小基線集(SBAS, small baseline subset)方法克服時間、空間的限制性，獲取連續的震後形變時間序列，影像從震後三個月至兩年後，結果顯示地震附近地區每年以約8-10mm的量持續下陷，震後時間序列除了顯示當雄地震所造成的震後形變外，也包含了凍土所造成的季節性震盪，且溫度的變化造成凍土的凍脹和融沈對地形的起伏影響，超過超過震後形變量，因此對青藏高原地區進行形變監測，必須將凍土變化量的因素考慮進去。;Tibet Plateau (TP) is one of the most prominent and tectonically active region in the world. This region was formed as a process of continent collision between the Indo-Australian and Eurasian Plate. A series of rifts was developed on the TP. The Yadong-Gulu rift extending about 500km is the longest of the seven rifts. It is located in the east of convergence zone about ~100 km north of Lhasa, one of the most populous towns over TP. Since 1264 A.D., the Yadong-Gulu rift has experienced frequent large earthquakes. In 2008, an Mw 6.3 earthquake occurred in Dangxiong county near Yangyi graben, which is in the northern section of Yadong-Gulu rift. In this study, we use the synthetic aperture radar (SAR) data of L-band ALOS PALSAR with a long wavelength (23.6 cm) to mitigate the problem of coherence loss in rugged terrain. The interferometric result shows a significant coseismic deformation occurred near the epicenter with a maximum displacement of 30 cm along the line of sight (LOS) of the satellite. We produce a time series of post-seismic deformation from 2008 to 2011 by small-baseline subset (SBAS) method. According to the result, we found that there has obviously seasonal oscillations associated with freezing-thawing cycle of Tibet Plateau. After deducting seasonal oscillations impact, the maximum LOS displacement is around 10 mm per year after the earthquake and still continuing.
