Repeated catastrophic valley infill following medieval earthquakes in the Nepal Himalaya
Repeated catastrophic valley infill following medieval earthquakes in the Nepal Himalaya
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DOI：
10.1126/science.aac9865
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发表时间：
2016-01-08
期刊：
影响因子：
56.9
通讯作者：
Korup, Oliver
中科院分区：
文献类型：
--
作者：
Schwanghart, Wolfgang;Bernhardt, Anne;Korup, Oliver
过去喜马拉雅山大地震的地貌足迹是难以捉摸的，虽然他们迫切需要测量和预测地震扰动山地景观的恢复时间。我们目前的证据表明，灾难性的山谷填充后，至少有三个中世纪的地震在尼泊尔喜马拉雅山。在尼泊尔第二大城市博卡拉附近的细颗粒支流沉积物中，泥炭层、植物宏体化石和腐殖粉的放射性碳年代测定与附近类似于公元1100年、1255年和1344年的8级以上地震的时间相吻合。支流河谷的上游倾斜和其物源的x射线荧光光谱法排除了当地的来源。相反，地貌和沉积证据与灾难性的河流加积和泥石流相一致，这些河流加积和泥石流堵塞了几条支流，数十米长的钙质沉积物来自60公里外的高喜马拉雅源头。
Geomorphic footprints of past large Himalayan earthquakes are elusive, although they are urgently needed for gauging and predicting recovery times of seismically perturbed mountain landscapes. We present evidence of catastrophic valley infill following at least three medieval earthquakes in the Nepal Himalaya. Radiocarbon dates from peat beds, plant macrofossils, and humic silts in fine-grained tributary sediments near Pokhara, Nepal's second-largest city, match the timing of nearby M > 8 earthquakes in similar to 1100, 1255, and 1344 C.E. The upstream dip of tributary valley fills and x-ray fluorescence spectrometry of their provenance rule out local sources. Instead, geomorphic and sedimentary evidence is consistent with catastrophic fluvial aggradation and debris flows that had plugged several tributaries with tens of meters of calcareous sediment from a Higher Himalayan source >60 kilometers away.