A Long-term Surface Deformation Monitoring over Datun Volcano Group Using PS-InSAR Technique

大屯火山群為台灣地區最大之火山群，為了解此火山群之運動情況，已有許多研究單位於此區進行許多內部岩漿庫與外部地表之監測，由近年研究發現，大屯火山群仍含有活動之岩漿庫，為一休眠之活火山，由於大屯火山之地理位置接近台北盆地，若火山噴發即會造成嚴重之傷害，故對於大屯火山之監測，為刻不容緩之課題。遙感探測（Remote Sensing）技術為偵測地表形變常用之方法，其中的合成孔徑雷達干涉（InSAR）與合成孔徑雷達差分干涉（D-InSAR）技術具有大範圍獲取地表形變資訊，並可達公分等級精度之優點，但由於植被和山區之同調性較低，難以獲取形變資訊，為突破此限制，學者提出以永久散射體合成孔徑雷達差分干涉（PS-InSAR）技術偵測地表形變。本研究之目的為獲取長時間序列大屯火山外部地表形變資訊，而由於研究區域位於山區且植被覆蓋茂盛，影響InSAR與D-InSAR技術之偵測成果，故本研究實施PS-InSAR技術偵測單點之地表形變量，並使用ERS-2、ASAR、PALSAR三種衛星影像，組成1995年至2011年之長時間序列，得到時間序列內永久散射點之地表形變平均速度場（Velocity Field），發現大屯火山群上之地表形變，在同一地區並非持續的抬升或沉降，而存有隨時間、空間之不同，地表形變不規則之情況，本研究將此成果與GPS與精密水準資料檢核，得到趨勢符合真實地表形變情形之成果，證實以PS-InSAR技術偵測大屯火山群之能力。Although there was no eruption occurring for three hundred thousand years, the existing ground monitoring reveals that Datun volcanoes may be still active. As Datun volcano group is very close to Taipei City, serious damages would occur if the volcanoes erupted. Therefore it is critical to understand the behaviors of the volcanoes. To this end, we used space-borne Synthetic Aperture Radar (SAR) data and interferometric processing techniques to detect sub-centimeter level ground deformation. Moreover, in order to achieve a long term monitoring, multiple radar data, including ERS-2, ASAR and PALSAR covering from 1995 to 2011, were employed. Through the Persistent Scatterers Interferometric SAR (PS-InSAR) processing, the ground displacement rate occurring over Datun volcanoes was derived. We notice that ground displacement over Datun volcano group is inconsistence with time. The results were verified with ground leveling data and GPS observations and were proved reliable