集集地震後多時序邊坡崩塌特性變遷分析

Time Series Analysis of Landslide Evolution after Chi-Chi Earthquake

江定國(Ting-Kuo Chiang)

指導教授 ： 林美聆

國立臺灣大學/工學院/土木工程學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.00083

摘要

台灣位於板塊交界帶，盛行造山運動，地形陡峻、地質破碎複雜。因同時受到強降雨與大地震的作用，邊坡崩塌時有所聞。集集地震後，颱風豪雨事件引致崩塌破壞規模擴大，且崩塌反覆發生情況更為嚴重。降雨引致的崩塌災害一再復發，可能與地震長期效應有關，而引發崩塌災害之門檻雨量隨邊坡逐漸穩定而提高。故藉由分析多期事件崩塌變遷情形、建立致災門檻雨量變化趨勢，以瞭解地震對於崩塌災害發生的長期影響。
　　研究上利用多期已校正之災後遙測影像，以人工圈繪崩塌地。相關崩塌影響因子選定並建立其資料庫後，進行崩塌變遷分析與統計處理，將各期崩塌地區分成地震復發與非地震復發類型，以探討崩塌變遷及地震效應。針對災害事件進行雨場分割篩選並分析門檻雨量變化，與崩塌變遷分析結果相互驗證。最後由案例分析輔助探討整體崩塌分析之成果。
本研究區眉溪流域中，由各因子崩塌變遷分析地震效應衰減趨勢，其中坡度、區位與殘土率分析可推定地震影響約在震後5~7年開始明顯減弱；雨量變異分析可發現震後約1~5年致災門檻雨量明顯偏低，約8~9年則明顯提高，顯示此時邊坡已趨穩定；案例驗證結果說明，部份符合各崩塌因子分析之變遷趨勢，但因案例所在獨特自然環境條件因素，使崩塌發育分析結果不盡相同。

關鍵字

邊坡崩塌 ； 崩塌變遷分析 ； 集集地震 ； 多時序 ； 門檻雨量

並列摘要

Taiwan is located in the junction of tectonic plates, which causes complex and fragile geological conditions. The hazardous landslides were often induced by heavy rainfall and great earthquake. After Chi-Chi earthquake, landslides in Taiwan have been repeatedly reactivated more severely by typhoons due to the prolonged effect of earthquake. The threshold rainfall inducing landslides should increase gradually as the slopes become more stable with time proceeds. Therefore, study of the time series evolution of landslides and the variation of threshold rainfall could evaluate the influence of Chi-Chi earthquake on landslide disasters.
In this research, time series remote-sensing images and DTM data were collected and corrected, for the interpretation of landslides by artificially and the establishment of selected landslide casual factors database. In analysis of landslides evolution, the landslides were distinguished into earthquake-reactivated type and non-earthquake -reactivated type for further discussion. Then rainfall analysis focusing on disaster events was performed to evaluate the threshold rainfall variation, for the validation of landslide evolution analysis. Finally, case study was included, in order to assist the discussion of the landslide evolution.
In the May River basin, our inference is that the prolonged effect of Chi-Chi earthquake on landslides sustained about 5~7 years according to the landslide evolution analysis. Also, we found that the slopes become stable about 8~9 years after Chi-Chi earthquake by the rainfall variation analysis, which is consistent with the results above. But the results of case study did not fully correspond with the analysis of overall landslides evolution, which may due to landslides occurrence has unique environmental condition.

並列關鍵字

slope landslide ； landslides evolution analysis ； Chi-Chi earthquake ； time series ； threshold rainfall

參考文獻

[40] 李馨慈 (2010)，重大地震地表擾動衰減特性於震後高強度降雨之山崩潛勢分析，國立成功大學資源工程學系博士論文。

[41] 吳翊鼎 (2007)，集集大地震對陳有蘭溪流域邊坡穩定之影響，國立台灣大學地理環境資源研究所碩士論文。

[44] 林文賜 (2009)，集水區自動劃分理論之評估與應用，水保技術，4(2):74-80。

[45] 洪如江 (1997)，台灣地區工程地質分區分佈圖。

[46] 洪如江、林美聆、陳天建、王國隆 (2000)，921集集大地震相關坡地災害、坡地破壞特性與案例分析，地工技術，第81期，第17-32頁。