台灣西南部淺層活動斷層潛移速率變化：利用InSAR與GNSS進行分析

Abstract

活動構造在地震周期中透過潛移釋放應力，其變形速率可能會因為地震觸發或泥貫入體的活動而有所改變。這樣的潛移斷層可能對基礎建設造成破壞，也會影響區域地震災害潛勢的評估。台灣西南部位於歐亞板塊和菲律賓海板塊之間的碰撞帶造山前緣，構造活動頻繁，對包括台南與高雄在內的數百萬居民構成威脅。該地區擁有眾多活動斷層，其中有些在2010年Mw 6.3的甲仙地震和2016年Mw 6.4的美濃地震中受到了顯著影響。這些地震觸發了一些先前未充分瞭解的淺層構造活動，分析這些構造在不同時期的滑移速率是一個相當重要的研究課題。 合成孔徑雷達干涉測量技術（InSAR）具有高空間解析度的優勢，近年來在測地領域中相當具有影響力。在本研究中，我使用ALOS與ALOS-2兩組L波段合成孔徑雷達衛星影像，產製台灣西南部的地表變形速度場，這些波長較長的雷達影像即使在植被茂密的台灣南部丘陵地區也能得到良好的成果。本研究建立了2007-2010年和2015-2022年兩個時段的地表間震變形速度場，以及2016美濃地震的同震地表變形場，這些結果都與連續GNSS測站的觀察成果有良好的相關性。 研究結果顯示，在新化斷層與屏東平原之間存在15條具有顯著變形量差異的速率邊界，其中部分與後甲里斷層、小崗山斷層、右昌斷層、龍船背斜等前人熟知的淺部活動構造相符；此外，還在過去研究較少涉及的區域發現了一些新的線狀構造，顯示台灣西南部的淺層活動構造仍有許多尚未充分瞭解之處。透過InSAR和水準測量資料的剖面分析，本研究成功辨識出一些構造在不同的觀測時間段內潛移速率有明顯變化，本研究取得的成果不僅有助於評估台灣西南部的地震災害潛勢，還為研究活動構造在地震週期中的潛移變形現象提供了重要線索，突顯了持續監測與深入研究的必要性。

The creeping behavior of active faults play a critical role in stress release during the seismic cycle, with their deformation rates potentially influenced by earthquake triggering or the activity of mud diapir. Such creeping faults not only pose a risk to infrastructure but also significantly impact the assessment of regional seismic hazard potential. Southwestern Taiwan is located at the orogenic front formed by the arc-continent collision between the Eurasian Plate and the Philippine Sea Plate, many active structures in this area pose significant threats to the lives and property of millions of residents in Tainan and Kaohsiung. Two large earthquakes, the 2010 Mw 6.3 Jiashian earthquake, and the 2016 Mw 6.4 Meinong earthquake, occurred in Southwestern Taiwan. These earthquakes triggered shallow fault activity and some of them was not well understood in the previous studies. One important question is how surface deformation changes in response to the earthquakes during the interseismic period. Recently, the Interferometric Synthetic Aperture Radar (InSAR) technique has become a more influential geodetic method for accessing high spatial resolution deformation patterns. In this study, I used L-band SAR images from the ALOS and ALOS-2 satellites to generate ground deformation velocity fields for Southwestern Taiwan. The longer wavelength of these radar images enabled effective monitoring even in the densely vegetated hill regions of southern Taiwan. I constructed interseismic surface deformation velocity fields for the periods of 2007-2010 and 2015-2022, as well as coseismic deformation fields for the 2016 Meinong earthquake, all of which showed strong correlation with continuous GNSS station data. The results revealed 15 velocity boundaries with clear deformation gradient in the region between the Hsinhua Fault and the Pingtung Plain. Some of which correspond to previously known shallow active structures such as the Houchiali Fault, Hsiaokangshan Fault, Youchang Fault, and Lungchuan Anticline, while other linear features identified in regions with less addressed in previous studies, highlighting that many shallow active structures in Southwestern Taiwan remain poorly understood. Through the profile analysis of InSAR and leveling data, this study successfully identified variations in interseismic slip rates across different time periods. The findings not only contribute to the assessment of seismic hazard potential in Southwestern Taiwan, but also provide critical insights into the creeping behavior of active structures throughout the seismic cycle, emphasizing the need for continuous monitoring and further investigation.