海底地滑：台灣西南海域手掌海脊個案研究;A Submarine Landslide Case Study from Palm Ridge, Offshore Southwestern Taiwan

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题名:	海底地滑：台灣西南海域手掌海脊個案研究;A Submarine Landslide Case Study from Palm Ridge, Offshore Southwestern Taiwan
作者:	凡古源;Van, Nguyen Trong
贡献者:	應用地質研究所
关键词:	海底地滑;邊坡穩定分析;超額孔隙水壓;地震;天然氣水合物分解;Submarine landslide;slope stability analysis;excess pore water pressure;earthquakes;gas hydrate dissociation
日期:	2019-01-22
上传时间:	2019-04-02 15:13:40 (UTC+8)
出版者:	國立中央大學
摘要:	海底地滑不只是控制海底地形和傳輸沉積物至深水環境中，且對人類生命有巨大的影響。手掌海脊位於被動和活動大陸邊緣之間，根據過去研究，這裡曾發生海底事件，這事件與歷史事件中1781/1782年海嘯事件有高度相關。然而，海底地滑的發生仍未被充分研究。基於高解析度多波束測探系統、反射震測剖面和海底淺層數據，本研究旨在確定研究區域內是否存在古代海底地滑。若地滑確實存在，就能建立地滑的3D模型。此外，無限邊坡穩定分析來評估地震的可能大小和天然氣水合物分解產生的超額孔隙壓力的量。上述兩者被認為是最合理的滑坡觸發因子，透過常用的ArcGIS和Fledermaus技術來預測和繪製地滑範圍，然後通過地球物理探勘數據驗證確定的範圍。並使用Topo to Raster插值演算法重建事件前地形。初步成果顯示，研究區域內曾發生巨大的海底地滑，其長度約為22公里，寬6公里，覆蓋總面積為90.76平方公里。破壞面的最大深度沿代表剖面為296公尺，平均深度為162公尺。此海底地滑釋出並沉積大量沉積物，估計體積分別為4.02和4.9立方公里。無限邊坡穩定分析法表明，觸發滑坡破壞所需的超額孔隙壓力為1044 kPa，所需的尖峰地面加速度範圍為0.11至0.28 g。關鍵字：海底地滑、邊坡穩定分析、超額孔隙水壓、地震、天然氣水合物分解. ;Submarine landslides do not only regulate the shape of the seafloor and transport sediment into the deep-water environment, but also have a significant influence on human life. Palm Ridge is an area located between passive and active continental margin. According to previous studies, there could be a submarine event occurred in this area. That event also considered highly related to the 1781/1782 tsunami event described in the historical records. However, the occurrence of that submarine landslide is still not well-studied. Based on the high-resolution multi-beam bathymetric, reflection seismic profiles and sub-bottom data, this study aims to confirm that whether there is an ancient submarine landslide in the study area or not. If the landslide does exist, then the 3D model for the proposed landslide will be built. In addition, an infinite slope stability analysis method will be applied to evaluate the possible magnitude of an earthquake and the amount of excess pore pressure resulting from gas-hydrate dissociation. They are considered as the most plausible landslide triggering factors. Utilizing the common use of ArcGIS and Fledermaus techniques, the range of landslide is predicted and mapped and then the identified range is validated by the geophysical prospecting data. The pre-event topography is also reconstructed by using Topo to Raster interpolation algorithm. The preliminary result shows that there is a huge submarine landslide occurred in the study area with the dimension of roughly 22 km length, 6 km wide and covering a total area of 90.76 km2. The maximum depth of the failure surface along the representative cross section is about 296 m and the average depth is 162 m. This submarine landslide released and deposited a huge amount of sediment with an estimated volume of 4.02 and 4.9 km3, respectively. The infinite slope analysis indicated that the required amount of excess pore pressure to trigger the failure of slope is 1044 kPa. And the required Peak Ground Acceleration ranges from 0.11 to 0.28g.
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