埔里盆地位於西部麓山帶和雪山山脈之間，是台灣活躍造山帶中面積最大的山間盆地。埔里盆地，與其南邊一系列沿北北東走向分佈的小盆地的發育和地下構造應有密切相關，推測此處為構造運動的轉變帶。本研究以衛星雷達量測地表變形，配合野外調察以瞭解及分析埔里盆地及周圍地區的構造及其活動特性。由於埔里盆地為群山環繞，陡峭的地形以及茂密的植被造成一般的衛星測量技術難以進行，本研究使用的永久散射體差分干涉技術克服以上障礙以監測長期地殼變形。我們使用歐洲太空總署的ERS-1和ERS-2衛星於1993-2002年間拍攝的影像，以及Envisat衛星於2004-2008年間拍攝台灣中部一系列的影像，進行分析與討論。結果顯示埔里盆地的衛星視角速度相對其他地區較低，表示埔里盆地的運動方向正遠離衛星，這可能代表盆地西側的滑脫面上有一斷坡構造，滑脫面在盆地下方有向下變深的現象，使得地表的運動方向有所改變。為了解釋台灣中部地表變形的機制，我們以前人研究的構造模型為依據，利用模型正演來檢驗地下構造和地表變形的關係，並逐一討論之。本研究亦將衛星觀測結果與全球衛星定位系統和精密水準測量資料結合，並配合野外調查了解構造實際出露位置及其活動特性，初步結果推測埔里盆地是由於滑脫帶上的斷坡構造活動時造成盆地相對陷落。此外今年三月二十七日及六月二日的南投地震及其餘震分布可以發現盆地下部除的滑脫構造面外還存在和另一共軛的斷層系統，初步推測此共軛斷層系統和埔里盆地群的形成有一定的關連，為未來值得深入研究的主題。 The Puli Basin, located between the Western Foothills and the Hs?ehshan Range is the largest basin in the active orogeny in central Taiwan. South to the Puli Basin, a series of small basins spread along the SSW direction. These basins, along with the Puli Basin itself, may be formed at a kinematic transition zone, which makes the tectonic of Puli Basin complicated. Various tectonic models have been proposed in previous studies to interpret the formation of the Puli Basin. In this study, we aim to measure the deformation and to understand the tectonics of Puli Basin by the method of satellite remote sensing and field observation. Since the Puli Basin is bordered by the mountains with steep topography and dense vegetation, we applied the Persistent Scatterer Interferometric SAR technique to monitor the surface deformation. We chose the ERS-1 and ERS-2 SAR images acquired in 1993-2002 and Envisat images acquired in 2004-2008 covering the central Taiwan area to carry out a series of analysis. Our result shows a relative lower LOS velocity in Puli Basin, which implies the change of depth of the subsurface basal detachment. A steep ramp along the detachment is proposed for the grown structure underneath the Puli Basin in this study. In order to interpret the mechanism of surface deformation in central Taiwan, we implement several forward models based on previous researches and our interferometric results and then compare our observations with accurate GPS and precise leveling data. These results can be compared with our field observations and with the recent seismicity data (327 and 602 aftershocks of this year) to examine the activity and geometry of faults of this area, where a conjugate fault system below the basins was suggested. Due to the lack of evidence, however it is hard to determine the relationship between the conjugate system and the basin subsidence mechanism. It is an interesting and worthwhile work for the further research to understand the tectonic activity in central Taiwan.
