High Resolution Radar Imaging of Pyroclastic Density Currents

火山碎屑密度流的高分辨率雷达成像

• 批准号: NE/T008253/1
• 负责人: Jim McElwaine
• 金额: $ 98.82万
• 依托单位: Durham University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FT008253%2F1
• 关键词: Resolution; Radar; Imaging; Pyroclastic; Density

Pyroclastic density currents (PDCs) are clouds of ash and rock, generated during eruptions, which propagate down volcanoes at high speed. They are the major hazard at many active volcanoes and have killed thousands of people. Our current ability to predict their behaviour and plan for their effects is limited, in part, by our incomplete knowledge of their flow dynamics. The proposed research will revolutionise our understanding of PDCs by obtaining, for the first time ever, measurements of position in time, hence velocity, of the dense core of moving PDCs using an advanced custom-built radar system (GEODAR). GEODAR has been developed and successfully used on snow avalanches, dramatically improving our knowledge of their dynamics. The project will build and deploy three GEODAR systems that have a spatial range resolution of 0.375 m and will image the dense core flow at 100 Hz: a spatial and time resolution never achieved before in studies of PDCs. GEODAR will easily penetrate the ash cloud to image the dense, destructive underflow, and can observe all particles larger than 30 mm. This novel system will be able to track PDCs along their flow paths and will allow us to image internal surges, roll-waves and flow fronts and reconstruct the velocity structure of moving PDCs. This data will enable the rigorous testing of PDC flow models and provide fundamental insights into their flow so that improved models can be developed. In addition, the flow path and deposits of the PDCs will be digitally mapped by a drone at 30 mm resolution in order to resolve the lateral extent and location of the flow. Features in the digital terrain maps will be directly matched with the features observed in the radar data and this will greatly add to the understanding of PDC emplacement mechanisms. For some flows we expect to have high resolution DTMs both before and after the event, and we will produce erosion and deposition maps. This data feeds in to the final part of the project which is the computer simulation of PDCs. The simulation code produces will be useful for predicting the path and forces of PDCs which is necessary for saving lives and protecting infrastructure. The code will be made freely available and a workshop run on its use. The DTM will be used for running the SHALTOP code and the results will be compared with GEODAR data and the erosion and deposition maps. SHALTOP is a simulation code developed, over the past fifteen years, by a French team partner in this project. It can be run with a variety of flow laws and we will determine which flow law best matches the data and from there we develop improvements. Such a detailed comparison has never been done before due to the lack of data from flowing PDCs. We have chosen Santiaguito volcano, Guatemala, as the test site. It is one of the world's most active volcanoes, which has been erupting since 1922 and dozens of PDCs are generated every year. The team has extensive experience working at this site and the local volcano observatory is an enthusiastic participant in the project. In addition, the terrain around the volcano is ideally suited for the location of GEODAR, with nearly complete sight-lines to the likely flow paths. The systems will be remotely triggered using a combination of infrasound and seismic signals. The three GEODAR systems will be stand- alone solar-powered units and communicate via a satellite-phone data link. The data storage will be on SSDs mounted in fireproof crash boxes so that they can withstand inundation.This research will produce the first ever high resolution position, and hence velocity, data for the dense core of flowing PDCs and the first ever model comparison with such data. The project will develop improved theoretical and computational models for PDCs and improve the accuracy of hazard assessments around volcanoes. The ultimate aim is to improve physical knowledge of these destructive natural hazards with the potential to save hundreds of lives.

火山碎屑密度流 (PDC) 是火山喷发期间产生的火山灰和岩石云，它们沿着火山高速传播。它们是许多活火山的主要危害，已造成数千人死亡。我们目前预测其行为和计划其影响的能力受到限制，部分原因是我们对其流动动力学的了解不完整。拟议的研究将通过使用先进的定制雷达系统（GEODAR）首次获得移动 PDC 密集核心的时间位置测量，从而彻底改变我们对 PDC 的理解。 GEODAR 已经开发出来并成功用于雪崩研究，极大地提高了我们对雪崩动力学的了解。该项目将建造和部署三个空间距离分辨率为 0.375 m 的 GEODAR 系统，并将以 100 Hz 的频率对密集核心流进行成像：这是 PDC 研究中从未达到的空间和时间分辨率。 GEODAR 可以轻松穿透灰云，对密集的、破坏性的底流进行成像，并可以观察所有大于 30 毫米的颗粒。这种新颖的系统将能够沿着 PDC 的流动路径进行跟踪，并使我们能够对内部浪涌、滚波和流动前沿进行成像，并重建移动 PDC 的速度结构。这些数据将使 PDC 流动模型能够进行严格的测试，并提供对其流动的基本见解，以便开发改进的模型。此外，无人机将以 30 毫米分辨率对 PDC 的流动路径和沉积物进行数字绘制，以解析流动的横向范围和位置。数字地形地图中的特征将直接与雷达数据中观察到的特征相匹配，这将极大地增加对 PDC 安置机制的理解。对于某些流量，我们希望在事件发生之前和之后都有高分辨率 DTM，并且我们将生成侵蚀和沉积图。该数据将输入项目的最后部分，即 PDC 的计算机模拟。生成的模拟代码将有助于预测 PDC 的路径和力量，这对于拯救生命和保护基础设施至关重要。该代码将免费提供，并举办一个关于其使用的研讨会。 DTM 将用于运行 SHALTOP 代码，并将结果与​​ GEODAR 数据以及侵蚀和沉积图进行比较。 SHALTOP 是由该项目的法国团队合作伙伴在过去十五年中开发的模拟代码。它可以使用各种流动定律运行，我们将确定哪种流动定律最适合数据，并据此进行改进。由于缺乏流动 PDC 的数据，以前从未进行过如此详细的比较。我们选择了危地马拉的圣蒂亚吉托火山作为试验地点。它是世界上最活跃的火山之一，自1922年以来一直在喷发，每年都会产生数十座PDC。该团队在该地点拥有丰富的工作经验，当地火山观测站也是该项目的热情参与者。此外，火山周围的地形非常适合 GEODAR 的位置，几乎可以看到可能的流动路径。该系统将使用次声和地震信号的组合进行远程触发。三个 GEODAR 系统将是独立的太阳能装置，并通过卫星电话数据链路进行通信。数据存储将存储在安装在防火防撞盒中的 SSD 上，以便能够承受洪水。这项研究将产生有史以来第一个高分辨率位置数据，从而产生流动 PDC 密集核心的速度数据，并首次与这些数据进行模型比较。该项目将为 PDC 开发改进的理论和计算模型，并提高火山周围灾害评估的准确性。最终目标是提高对这些破坏性自然灾害的认识，有可能挽救数百人的生命。