檢驗SBAS-InSAR於2016年美濃地震震後變形分析

Examining SBAS-InSAR Analysis for Postseismic Deformation of 2016 Meinong Earthquake

劉婉姿(Wan-Tzu Liu)

指導教授 ： 莊昀叡

國立臺灣大學/理學院/地理環境資源學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202000615

摘要

在干涉合成孔徑雷達的時間序列技術出現之後，由於干涉合成孔徑雷達提供了具有高空間分辨率和大覆蓋範圍的快速、例行觀測，因此地表變形監測的發展得到了顯著改善，干涉合成孔徑雷達時間序列技術的一項主要應用即是震後變形觀測。震後變形會呈現非線性的速率衰變，在GPS分析中是透過時間序列擬合將震後變形訊號獨立取出，然而許多使用干涉合成孔徑雷達時間序列技術對於震後研究則常有不同的估計震後變形的方法。因此，本研究將小基線子集–干涉合成孔徑雷達技術應用於2016年的美濃地震，以檢驗干涉合成孔徑雷達時間序列應用於震後變形的過程。美濃地震是在Sentiniel-1衛星發射後臺灣近年具有大範圍震後變形的地震之一。作為參考，本研究首先擬合2007-2018年的GPS時間序列，以確定每個GPS站的地震前和地震後訊號。接著檢驗大氣校正、空間校正和干涉合成孔徑雷達時間序列擬合等不同方法的結果。本研究比較GMTSAR和GACOS的大氣校正方法；線性擬合、超平面和插值的空間校正方法；以及使用GPS或InSAR震前速度進行的時間序列擬合。結果顯示干涉合成孔徑雷達時間序列過程中的不同方法將影響震後變形的訊號。GMTSAR大氣校正結果比GACOS校正結果好，因為GACOS資料來源時間解析度差。內插空間校正的結果比線性擬合與超平面空間校正好，原因是區域的地表變形位移量並不相同。震前GPS速度因為資料時間較長得到的速率較穩定，因此較適合用來時間序列擬合。因此GMTSAR大氣校正，內插空間校正和使用震前GPS速度的InSAR時間序列擬合可以提供更合理的震後模式。

關鍵字

全球衛星導航系統 ； 雷達 ； 地震周期循環 ； 地表速度

並列摘要

After the appearance of time-series techniques of interferometric synthetic aperture radar (InSAR), the development of surface deformation monitoring has significantly improved since InSAR provides fast, routine observations with high spatial resolution and coverage. One major application of the time-series InSAR techniques is postseismic deformation detection. Because postseismic deformation shows the pattern of non-linear velocity decay, in GPS analysis one can differentiate the postseismic signals by fitting GPS time series while in InSAR time series analysis the method to estimate the postseismic deformation varied in many studies. Therefore, this study uses the small baseline subset InSAR (SBAS-InSAR) technique for the 2016 Meinong earthquake, which is one of recent strong earthquakes in Taiwan with wide-ranging postseismic deformation after the operation of Sentiniel-1 satellite, to examine the process of time-series InSAR for postseismic deformation. For reference, this study first fits GPS time series of 2007-2018 to determine preseismic and postseismic signals at each GPS stations, and examines the results of different methods for atmospheric correction, spatial correction and InSAR time-series fitting. This study compares atmospheric correction methods of GMTSAR and GACOS, spatial correction methods of linear fitting, hyperplane and interpolation, and time series fitting by using GPS or InSAR preseismic velocities. The results suggest that different methods in the procedure will influence the isolation of postseismic signals. The GMTSAR atmospheric correction results are better than GACOS correction results, because GACOS data sources have poor time resolution. The results of interpolation are better than the linear fitting and hyperplane, because the surface deformation in the study area is spatially inhomogenous. The preseismic GPS velocity is more stable than InSAR velocity because of longer observation time, so it is more suitable for time series fitting. Therefore, the GMTSAR atmospheric correction, interpolation spatial correction, and time-series fitting with preseismic GPS velocities can provide more reasonable postseismic pattern.

並列關鍵字

GNSS ； radar ； earthquake cycle ； surface velocity

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