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New insights into the deposit architecture and emplacement mechanisms of block-and-ash flows using ground penetrating radar

使用探地雷达对沉积物结构和块状灰流的安置机制的新见解

基本信息

批准号：
NE/F000936/1
负责人：
Ralf Gertisser
金额：
$ 8.88万
依托单位：
Keele University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2008
资助国家：
英国
起止时间：
2008 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FF000936%2F1
关键词：
New insights into deposit architecture

项目摘要

Block-and-ash flows (BAFs) are amongst the most dangerous volcanic phenomena on the planet. Generated by gravitational or explosive collapses of viscous lava domes or by the collapse of vulcanian-type eruption columns, BAFs are common at many active subduction zone volcanoes, including Colima (Mexico), Unzen (Japan), Soufrière Hills (Montserrat), Arenal (Costa Rica) and Merapi (Indonesia), where they pose a severe threat to the surrounding population and infrastructure. Merapi, an andesitic composite volcano located in Central Java (Indonesia), is one of the most frequently erupting volcanoes in Indonesia with nearly persistent volcanic activity. Of the 1.1 million people living on the flanks of the volcano, almost half live in high-risk areas. It is estimated that property worth tens of millions of U.S. dollars lies in the vulnerability zone of the volcano and this amount is likely to increase given a population growth rate of 3% per year in the local area. Since the mid-1500s, eruptions of Merapi have caused ~7000 fatalities. More recently, BAFs from a small-scale eruption in 1994 killed 66 people, whilst the renewed activity of 2006, which, for the first time in more than a century affected densely populated areas on the volcano's southern flank, led to more fatalities. These eruptions illustrate the unpredictable and still poorly understood behaviour of BAFs, which caused havoc in areas considered relatively save from BAFs and related hazards. Furthermore, they have demonstrated the urgent need for an improved physical understanding of the mobility, transport and deposition processes of BAFs in order to improve assessments of their local hazard potential. Traditionally, qualitative models of BAF transport and deposition have been developed based on interpretations of the internal structure from resulting deposits. Unfortunately, a combination of poor exposure and rapid lateral facies variations, controlled by unknown palaeo-topography, have often complicated such field-based studies and have hindered the detailed assessment of emplacement mechanisms and, hence, the hazard potential of such flows. This proposal aims to overcome the inherent limitations of these traditional studies through the application of ground penetrating radar (GPR) to the 2006 Merapi BAF deposits, which provide a unique and ideal natural laboratory for this type of research. The application of GPR to pyroclastic deposits is relatively new and the technique is capable of allowing systematic and rapid collection of sub-surface information independently from the presence of exposures. This opens a unique perspective that, when combined with detailed sedimentological studies along exposed sections, will provide the most complete picture yet of the three-dimensional deposit architecture of BAF deposits and how this type of pyroclastic flows is emplaced. Such a level of interpretational sophistication is impossible to achieve with direct observation techniques alone. The results of this study will be instrumental in formulating a new, improved understanding of BAF-related hazards and help provide sustainable technology solutions to the challenges associated with hazard mitigation (a priority area highlighted in the NERC Strategic Plan for Science). One of the key outcomes of the project is to create a unique, well-constrained data set that has important applications to the numerical modelling of mass flows and the emplacement dynamics of multi-phase granular deposits. Consequently, the work will be of immediate benefit to all groups involved in assessing volcano hazards either directly (at observatories on some of the most active volcanoes around the world) or through remote sensing and numerical modelling techniques.

块和灰流（BAF）是地球上最危险的火山现象之一。由于粘性熔岩穹丘的重力或爆炸性坍塌，或由于火山喷发柱的坍塌，生物活性泡沫在许多活跃的俯冲带火山中很常见，包括科利马（墨西哥）、云仙（日本）、苏弗里耶尔山（蒙特塞拉特）、阿纳尔（哥斯达黎加）和默拉皮（印度尼西亚），它们对周围的人口和基础设施构成严重威胁。默拉皮火山是位于印度尼西亚爪哇中部的一座安山质复合火山，是印度尼西亚最频繁喷发的火山之一，火山活动几乎持续不断。生活在火山两侧的110万人中，几乎一半生活在高风险地区。据估计，价值数千万美元的财产位于火山的脆弱区，鉴于当地每年3%的人口增长率，这一数额可能会增加。自1500年代中期以来，默拉皮火山爆发已造成约7000人死亡。最近，1994年的一次小规模火山爆发造成66人死亡，而2006年的重新活动，世纪以来第一次影响到火山南翼人口稠密的地区，导致更多的死亡。这些喷发说明生物活性炭的行为是不可预测的，而且人们对生物活性炭的行为仍然知之甚少，这些行为在被认为相对没有生物活性炭和相关危害的地区造成了严重破坏。此外，它们还表明，迫切需要更好地实际了解生物放大器的流动、迁移和沉积过程，以便更好地评估其在当地的潜在危害。传统上，定性模型BAF传输和沉积已开发的基础上解释的内部结构从所产生的存款。不幸的是，不良暴露和快速横向相变化的组合，由未知的古地形控制，往往复杂的实地研究，并阻碍了详细评估的定位机制，因此，这种流动的潜在危险。该提案旨在通过将探地雷达应用于2006年默拉皮生物活性炭矿床，克服这些传统研究的固有局限性，为这类研究提供了独特和理想的天然实验室。探地雷达在火山碎屑沉积物中的应用相对较新，该技术能够系统、快速地收集地下信息，而与暴露的存在无关。这打开了一个独特的视角，当结合详细的沉积学研究沿着暴露的部分，将提供最完整的图片还没有的三维存款架构的BAF存款和如何安置这种类型的火山碎屑流。这样一个水平的解释复杂性是不可能实现的直接观察技术。这项研究的结果将有助于制定一个新的，更好地了解生物曝气生物滤池相关的危害，并帮助提供可持续的技术解决方案，以应对与减灾相关的挑战（在NERC科学战略计划中强调的优先领域）。该项目的主要成果之一是创建一个独特的、约束良好的数据集，该数据集对质量流和多相颗粒矿床的就位动力学的数值建模具有重要应用。因此，这项工作将直接有益于直接（在世界上一些最活跃的火山的观测站）或通过遥感和数字建模技术参与评估火山危险的所有团体。