Processes beneath the Great Wave: improved understanding of tsunami geohazards using advances in deep-sea sedimentology

大浪之下的过程：利用深海沉积学的进步提高对海啸地质灾害的了解

• 批准号: 2887332
• 金额: --
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2887332
• 关键词: Processes; beneath; Great; Wave; improved

Tsunami pose a very significant hazard to coastal communities and infrastructure, as seen in the giant earthquake-generated tsunami that affected the Indian Ocean in 2004, and Japan in 2011. More recently, the eruption of the Tongan volcano Hunga Tonga-Hunga Ha'apai in early 2022 also led to a destructive tsunami with both local and far field effects. Understanding of such tsunami is complicated by their great rarity and very high magnitude, which makes measurements of their waves exceptionally problematic. Much of our knowledge is limited to the recognition of ancient tsunami deposits, based primarily on their run-in (maximum distance inland) and run-up (maximum height reached). Sedimentological information from such deposits is largely restricted to the overall grain-size of their deposits. Much of the evidence for the nature of tsunami waves is locked in these deposits, and yet we have lacked the knowledge to be able to read this until recently. Here we will adopt a new approach that utilises the huge recent advances in understanding of flows in the deep oceans, based purely on their deposits.Deep-sea deposits may seem an unlikely starting point for the study of tsunami, yet there are many surprising similarities. Sedimentation of sand-sized (and larger) material in the deep-sea is primarily the result of a class of flows that include turbidity currents and debris flows, collectively known as sediment gravity flows (SGFs). Such flows in the deep-sea are highly infrequent and very powerful, and thus we have very few measurements of actual currents, and even these are almost entirely restricted to the slope, rather than the basin floor. Even for these flows, we have a much better idea on velocity distributions than we do sediment concentrations, stratification in the vertical, and sediment composition. Consequently, our knowledge of these powerful underwater flows is dominantly obtained from their deposits. Over the past 10-15 years there has been a revolution in our understanding of these SGF deposits, and a realisation that they are not solely low-concentration, turbulent currents or high-concentration cohesive debris flows. We now recognise that there is a full spectrum of flows in terms of concentration, and cohesive strength, with a large range of 'transitional flows', and that individual flow events can show dramatic changes in flow properties both longitudinally, and over time at a given point. More recently, we have developed methods to be able to identify these different flow states, and to assess their flow evolution. The supervisory team have been at the forefront of these advances in deepwater sedimentology, and understanding the dynamics of transitional and high concentration flows. More recently we have undertaken a proof-of-concept study on tsunami deposits to examine the applicability of these deepwater approaches. In this research project, the student will sample known tsunami deposits in Japan and Scotland. We also aim to integrate both marine and terrestrial cores, as well as some shallow water multibeam datasets, from additional examples. These datasets will be used to document the character of the sedimentary record (particle size, shape, mineralogy) using the cutting edge equipment in the Sediment, Soil, and Pollutant Analysis Laboratory at the University of Leeds, to better understand the formative processes under the tsunami. There is huge potential to re-examine the sedimentology of tsunami deposits to tackle the associated geohazards, and improve the resilience of coastal communities and infrastructure.The principal aim of the proposed PhD project is to improve understanding of the geohazards associated with tsunami utilising new sedimentological understanding derived from concepts developed in deep-marine sediments.

海啸对沿海社区和基础设施造成了非常严重的危害，正如 2004 年影响印度洋和 2011 年影响日本的巨大地震引发的海啸所示。最近，汤加洪加汤加-洪加哈派火山喷发2022 年初还引发了一场具有局部和远场影响的破坏性海啸。由于此类海啸极其罕见且震级极高，因此对此类海啸的理解变得十分复杂，这使得海啸的测量变得异常困难。我们的大部分知识仅限于对古代海啸沉积物的认识，主要基于其进入（内陆最大距离）和上升（达到的最大高度）。来自此类矿床的沉积学信息在很大程度上仅限于其矿床的总体粒度。海啸波性质的大部分证据都锁定在这些沉积物中，但直到最近我们还缺乏能够解读这些证据的知识。在这里，我们将采用一种新方法，利用最近在理解深海流动方面取得的巨大进展，纯粹基于其沉积物。深海沉积物似乎不太可能是海啸研究的起点，但它们有许多令人惊讶的相似之处。深海中沙子大小（和更大）的物质的沉积主要是一类流动的结果，包括浊流和泥石流，统称为沉积物重力流（SGF）。深海中的这种水流非常罕见且非常强大，因此我们对实际水流的测量很少，即使这些水流也几乎完全局限于斜坡，而不是盆地底部。即使对于这些流动，我们对速度分布的了解也比对沉积物浓度、垂直分层和沉积物成分的了解要好得多。因此，我们对这些强大水下水流的了解主要是从它们的沉积物中获得的。在过去的 10-15 年里，我们对这些 SGF 沉积物的认识发生了革命，并认识到它们不仅仅是低浓度的湍流或高浓度的粘性泥石流。我们现在认识到，在浓度和内聚强度方面存在全谱的流动，具有大范围的“过渡流动”，并且单个流动事件可以在纵向和随时间的推移显示流动特性的巨大变化。给定点。最近，我们开发了能够识别这些不同流动状态并评估其流动演变的方法。监督团队一直处于深水沉积学进展的最前沿，并了解过渡流和高浓度流的动态。最近，我们对海啸沉积物进行了概念验证研究，以检验这些深水方法的适用性。在这个研究项目中，学生将对日本和苏格兰已知的海啸沉积物进行采样。我们还旨在整合来自其他示例的海洋和陆地核心以及一些浅水多波束数据集。这些数据集将用于使用利兹大学沉积物、土壤和污染物分析实验室的尖端设备来记录沉积记录的特征（颗粒大小、形状、矿物学），以更好地了解沉积物的形成过程。海啸。重新研究海啸沉积物的沉积学以解决相关的地质灾害并提高沿海社区和基础设施的恢复能力具有巨大的潜力。拟议的博士项目的主要目的是利用新的沉积学方法提高对与海啸相关的地质灾害的了解来自深海沉积物中发展的概念的理解。