Geochemical signatures up to the maximum inundation of the 2011 Tohoku-oki tsunami - Implications for the 869 AD Jogan and other palaeotsunamis
Geochemical signatures up to the maximum inundation of the 2011 Tohoku-oki tsunami - Implications for the 869 AD Jogan and other palaeotsunamis
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DOI：
10.1016/j.sedgeo.2012.05.021
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发表时间：
2012-12-30
影响因子：
2.8
通讯作者：
Nishimura, Yuichi
中科院分区：
文献类型：
--
作者：
Chague-Goff, Catherine;Andrew, Anita;Nishimura, Yuichi
在2011年3月11日海啸淹没仙台平原两个月、五个月和七个月后，对东北海啸沉积物和下伏土壤的地球化学特征进行了评估。可识别的沙子沉积物的范围被追踪到内陆2.9公里，而一个泥沙沉积物被发现在内陆4.65公里，分别占最大海啸淹没的60%和近95%。海啸发生两个月后，在没有任何沉积学证据的情况下，使用海洋地球化学标志物(S和氯)确定了距离海岸4.85公里处的海啸淹没界限。指示海洋入侵的其他地球化学标志物(K、Ca、Sr)和伴生矿物的浓度随陆地的变化而降低。三角洲C-13、三角洲N-15和C/N比值反映了沉积物中陆相和海相有机质的混合来源，而S-34硫酸盐三角洲反映了水溶盐的海相来源。公元869年Jogan海啸沉积的化学成分以高的锶和Rb含量为特征，与东北海啸沉积的化学成分相当，表明沉积物的来源可能是相似的。S和氯随时间的显著下降表明，降雨导致了沙质沉积物中盐分的淋失。然而，在海啸发生7个月后，S和氯标记物以及锶在泥质沉积物和下伏土壤中仍保存完好，超过了可识别的砂质沉积物的界限。这表明，通过确定超出可识别砂粒沉积界限的细粒沉积物的海洋来源，特别是在海洋微化石稀少或缺乏的情况下，特别是在仙台平原的情况下，地球化学指标在确定历史和古海洋沉积的范围方面可能非常有用。这将使研究人员能够重新绘制古海啸淹没地图，并重新评估不仅在仙台平原，而且在世界其他地方发生的Jogan海啸和其他古海啸的震级。这对海啸风险评估、减灾和备灾具有重要影响。(C)2012爱思唯尔B.V.保留所有权利。
The geochemical signature of the Tohoku-oki tsunami deposit and underlying soil was assessed two months, five months and seven months after the 11 March 2011 tsunami inundated the Sendai Plain. The extent of the recognisable sand deposit was traced up to 2.9 km inland while a mud deposit was found up to 4.65 km inland, representing 60% and nearly 95% of the maximum tsunami inundation, respectively. The limit of tsunami inundation was identified 4.85 km from the shore using geochemical marine markers (S and Cl) two months after the tsunami, in the absence of any sedimentological evidence. Concentrations of other geochemical markers (K, Ca, Sr) indicative of the marine incursion and associated minerals were found to decrease landward. delta C-13 and delta N-15 and C/N ratios suggested a mixture of terrestrial and marine organic sources in the sediment, while delta S-34 of sulphate reflected the marine source of water soluble salts. The chemical composition of the 869 AD Jogan tsunami sand deposit was characterised by high Sr and Rb concentrations and was comparable to that of the Tohoku-oki tsunami deposit, suggesting that the sources of sediment may be similar. Marked decreases in S and Cl with time indicated that rainfall resulted in the leaching of salts from the sandy sediments. However, both S and Cl markers as well as Sr were still well preserved in the muddy sediments and underlying soil beyond the limit of the recognisable sand deposit seven months after the tsunami. This suggests that geochemical indicators may well be useful in identifying the extent of historical and palaeotsunamis by determining the marine origin of fine grained sediments beyond the limit of recognisable sand deposition, in particular when marine microfossils are sparse or lacking as is the case on the Sendai Plain. This would allow researchers to redraw palaeotsunami inundation maps and re-assess the magnitude of events such as the Jogan tsunami and other palaeotsunamis, not only on the Sendai Plain but also elsewhere around the world. This has important implications for tsunami risk assessment, hazard mitigation and preparedness. (c) 2012 Elsevier B.V. All rights reserved.