Quantitative Analysis of Tsunami Disasters by The Jogan Earthquake

通过与海啸沉积物的粒度组成和相的类比，估计了869年Jogan地震海啸的沉积物输运模式。此外，还对海啸诱发水流的初始水力条件进行了沉积学评估，以增加对海啸抬高行为的了解。根据激光衍射粒度分析仪的粒度分析，清楚地确定了构成Jogan海啸沉积物的砂层向陆地细化。这与我们的泥沙输移和海啸沉积的水力学实验结果是一致的。阐明了沉积层的细化方式可以作为反映海啸抬升能量消散的重要指标。这些判据为从理论上理解海岸地形的形成提供了自然地理条件。此外，它们还可以为我们提供有关沿海地区城市和工业基础设施发展的不可或缺的知识。2004年印度洋海啸后有孔虫组合的变化通过对泰国西南海岸采集的沉积物样品的微古生物分析清楚地证明了这一点。这意味着在海底沉积环境中可以保存海啸反冲引起的浊流的痕迹。因此，通过对海洋沉积物的挖掘就有可能揭示海啸发生的历史。2007年7月在意大利佩鲁贾举行的IUGG第二十四届大会介绍了这些结果，并作为海啸灾害和沉积的实际例子得到了科学关注。

Mode of sediment transport by the 869 Jogan earthquake tsunami was estimated by analogy with grain-size composition and facies of the tsunami deposit. In addition, initial hydraulic condition of tsunami-induced currents was sedimentologically evaluated to increase knowledge on behavior of tsunami run-ups. Landward fining of the sand layer that comprises the Jogan tsunami deposit was clearly identified on the basis of the grain-size analysis by the laser-diffraction gram-size analyzer. This is consistent with the results from our hydraulic experiments of sediment transport and deposition of tsunamis. It is clarified that mode of fining of sedimentary layer can be treated as important criteria that reflect the energy dissipation of tsunami run-ups. These criteria may provide physical- geographic condition for theoretical understandings of formation of coastal topography. In addition, they may give us indispensable knowledge on developments of urban and industrial infrastructures of coastal areas.Changes in foraminiferal assemblages after the 2004 Indian Ocean tsunami were clearly demonstrated by the micropaleontological analysis of sediment samples collected from the southwest coast of Thailand. This implies that traces of turbidity currents induced by tsunami backwashes can be preserved in submarine sedimentary environments. Therefore history of tsunami occurrence is possible to uncover based on sediment excavation on the ocean. These results were presented and gained scientific attention in the XXIV General Assembly of IUGG that was held in Perugia, Italy, in July 2007, as an actual example of tsunami disaster and sedimentation.