Resolving tsunami wave dynamics: Integrating sedimentology and numerical modelling

IF 1.9 3区 地球科学 Q1 GEOLOGY
Jon Hill, Graham Rush, Jeff Peakall, Michael Johnson, Luke Hodson, Natasha L. M. Barlow, Elisabeth T. Bowman, W. Roland Gehrels, David M. Hodgson, Georges Kesserwani
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Abstract

Tsunamis are a major hazard along many of the world's coastlines. To understand the impact of these events, a sufficiently long record of previous events is needed, which can be provided by their sedimentary deposits. A number of past events have left extensive sedimentary deposits that can be used to understand the hydrodynamics of the tsunami. The ca 8.15 ka Storegga submarine slide was a large, tsunamigenic mass movement off the coast of Norway. The resulting tsunami had estimated run-up heights of around 10 to 20 m on the Norwegian coast, over 30 m in Shetland and 3 to 6 m on the Scottish mainland coast. New cores were taken from the Ythan Valley in North-East Scotland, where Storegga tsunami deposits have previously been found. High-resolution sedimentary analyses of the cores, combined with statistical (changepoint) analysis, shows signatures of multiple waves. Moreover, detailed CT scans of the erosional basal surface reveal sole marks called skim marks. Taken in conjunction with the grain size and sedimentary fabric characteristics of the tsunami deposits, this indicates that the flow exhibited a high-concentration basal component, with an initial semi-cohesive phase and that deposition was dominantly capacity driven. A multiple wave hypothesis is tested by creating a high-resolution numerical model (metre-scale) of the wave inundation, coupled to a previously published regional model. The inundation model confirms that multiple waves passed over the site in agreement with the sedimentological analysis. The sensitivity of the model to the reconstructed palaeocoastal geomorphology is quantitatively explored. It is concluded that local palaeogeomorphological reconstruction is key to understanding the hydrodynamics of a tsunami wave group in relation to its sedimentary deposit. Combining sedimentological data with high-resolution inundation modelling is a powerful tool to help interpret the sedimentary record of tsunami events and hence to improve knowledge of their risks.

Abstract Image

解决海啸波动力学:整合沉积学和数值模拟
海啸是世界许多海岸线上的一个重大灾害。为了了解这些事件的影响,需要对以前的事件进行足够长的记录,这些记录可以由它们的沉积沉积物提供。过去的一些事件留下了大量的沉积矿床,可以用来了解海啸的流体动力学。大约8.15卡的Storegga海底滑坡是挪威海岸附近一次大规模的海啸引发的大规模运动。据估计,由此引发的海啸在挪威海岸的上升高度约为10至20米,在设得兰超过30米,在苏格兰大陆海岸达到3至6米。新的岩芯取自苏格兰东北部的伊坦山谷,此前在那里发现了Storegga海啸矿床。岩心的高分辨率沉积分析,结合统计(变化点)分析,显示了多个波的特征。此外,侵蚀性基底面的详细CT扫描显示了被称为撇痕的足底痕迹。结合海啸沉积物的粒度和沉积组构特征,这表明流动表现出高浓度的基底成分,具有初始的半粘性相,并且沉积主要由容量驱动。通过创建波浪淹没的高分辨率数值模型(metrescale),结合之前发布的区域模型,对多波假设进行了测试。淹没模型证实,多个波浪经过现场,与沉积学分析一致。定量地探讨了该模型对重建的古海岸地貌的敏感性。结果表明,局部古地貌重建是了解海啸波群与其沉积矿床之间流体动力学关系的关键。将沉积学数据与高分辨率淹没建模相结合是一种强大的工具,有助于解释海啸事件的沉积记录,从而提高对其风险的认识。
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来源期刊
CiteScore
4.10
自引率
16.70%
发文量
42
审稿时长
16 weeks
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