考慮地震波之地形放大效應製作山崩潛勢圖

由實際量測資料及數值模型皆可發現，地震波能量由震源傳至地表處，位於山頂附近所接收到的能量會有放大的現象，相對的，位於山腳附近或河谷所接收到的能量會有縮小的現象發生，此因地表地形起伏所造成的地震強度分佈的變化，統稱為地形放大效應。傳統的地震引起之山崩潛勢分析，並無考慮此地形放大效應，此一結果造成山頂附近的地震強度有被低估的情況發生，本研究將此地形效應的影響納入山崩潛勢分析，製作更為完善的山崩潛勢圖。首先，利用研究區之數值高程模型建立波傳數值模型，計算出研究區之地形放大倍率，配合模擬地震加速度，計算出921集集地震之受地形效應影響地震強度，最後以Newmark位移分析法評估震後研究區之山崩危險指標，製作山崩潛勢圖。比對實際震後之山崩目錄資料，發現考慮地形效應後的山崩潛勢圖，其準確性高於傳統未考慮地形效應的山崩潛勢圖，因此，本研究發現，將地形效應的影響納入山崩潛勢分析的過程中，將有助於提高山崩潛勢分析的準確性。

關鍵字

山崩；地震；潛勢分析；地形效應； 921集集地震

並列摘要

It has been known that the seismic ground motion amplitude is amplified at topographic tops. However, such topographic effects are not included in conventional landslide hazard models. In this study, the topographic effect is incorporated in the seismic landslide hazard analysis. First, a 3D dynamic numerical model with irregular topography is constructed. The theoretical topographic amplification factors are derived from the dynamic numerical model. The reference motions are generated using the stochastic ground motion simulation technique. By combining the topographic amplification factors with the reference motions, the amplified acceleration time history and amplified seismic intensity parameters are generated. With these generated data, Newmark's displacement model is used to perform the seismic landslide hazard analysis. In order to evaluate the performance of the modified procedure, the Newmark's displacement maps of the Mt. Baishiya region, Nantou, Taiwan are constructed for landslide analysis. The landslide area triggered by the September 21, 1999, Chi-Chi earthquake is superimposed with the displacement maps. When compared to that of the conventional procedure, the modified method shows better ability for identifying the landslide areas.

並列關鍵字

Seismic hazards ； Newmark's method ； Topographic effect ； Landslides ； Earthquakes

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