Rapid-moving landslides occurred in many locations during the 2009 Padang earthquake, Sumatra. We interpreted satellite images, performed field surveys, in situ dynamic cone penetration tests, and laboratory analyses for mineralogy and physical and mechanical properties. We found that landslides occurred at 159 locations in an area of 64 km², and these areas had pumice fall deposits overlying paleosols which were heavily weathered debris flow deposits. These landslides in the investigated area occurred in areas with pumice fall deposits thicker than 350 cm; this depth was probably vital in inducing mechanical instability. The areas had sliding surfaces at the base of the pumice fall deposits, where pumice grains were mixed with the underlying paleosol and had been heavily weathered into halloysite-rich clayey materials by interaction with the percolating water from the ground surface. After the deposition of this pumice fall with mantle bedding, the beds were undercut by subsequent river erosion that loosen their downslope lateral support. This geologic history of pumice fall, weathering, and undercutting is not confined to the affected area but it is common to many volcanic areas, creating the opportunity to predict areas susceptible to earthquake-induced catastrophic debris avalanches.

在2009年苏门答腊巴东大地震期间，许多地方发生了快速滑坡。我们解释了卫星图像，进行了实地调查，进行了现场动态锥体渗透测试，并进行了矿物学以及物理和机械性能的实验室分析。我们发现滑坡发生在64 km ^2的159个位置，这些地区的浮石沉积物覆盖在古土壤之上，而古土壤是严重风化的泥石流沉积物。这些滑坡发生在被调查地区，其浮石沉积物的厚度超过350厘米。此深度可能对引起机械不稳定性至关重要。这些区域在浮石沉积物的底部具有滑动表面，浮石颗粒与下面的古土壤混合，并通过与来自地面的渗滤水相互作用而被强烈风化成富含埃洛石的黏土材料。在浮石被地幔垫层沉积后，这些床层被随后的河道侵蚀所侵蚀，从而削弱了它们的下坡侧向支撑。浮石掉落，风化和咬边的地质历史记录不仅限于受影响的地区，但在许多火山地区是常见的，