Predicting Lahar Evolution and Runout Behavior

预测泥浆演化和跳动行为

• 批准号: 0635778
• 负责人: Sarah Fagents
• 金额: $ 29.39万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-02-01 至 2011-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0635778&HistoricalAwards=false
• 关键词: Predicting; Lahar; Evolution; Runout; Behavior

Lahars are fast-flowing mixtures of water and volcanic rock fragments which have been responsible for some of the worst historical volcanic disasters. There is a wide spectrum of lahar types and processes, mostly linked to the relative volumes of water and rock particles. Existing models, needed for hazard forecasting deal well with the extremes of lahar behavior (floods and avalanches) but new models are needed to cover the wide middle ground for these complex phenomena, and to include the downstream evolution of a lahar and the implications for hazards to communities and infrastructure located in potential lahar pathways. Lahars can be triggered by heavy rainfall on loose volcanic deposits, by mixing of explosively erupted materials with water or ice, or by breakout of a summit crater lake. Most lahars have few warning signs and are thus essentially unpredictable. This study takes advantage of an almost unique situation where a breakout flood is predicted for the newly filled crater lake of Mount Ruapehu in New Zealand and will look to draw comparisons with Mount St Helens. The study, co-funded by the Petrology and Geochemistry and EPSCoR programs, will involve American and New Zealand scientists, students, and emergency managers in the production of a user-friendly hazard forecasting tool.The scientific approach involves integration of field data with computational modeling of lahar flow processes. The team will develop methods of describing mathematically the complex physical processes of lahars, and the manner in which their characteristics evolve as they flow away from source. This new model will be the first to tackle in detail additions and losses of sediment and water during the emplacement of a lahar, thus occupying a niche not well treated by existing mass flow models. Sediment entrainment processes have been found to be responsible for many-fold increases in flow volume, and thus are clearly important for understanding the magnitude of downstream hazard. Field studies at the two volcanoes will provide validation of the model, before application to a wider variety of volcanoes and lahar-triggering mechanisms. By packaging the end product as a user-friendly hazards forecasting tool, it is aimed to bridge the gap between lahar researchers and the communities that may directly benefit from this project.

火山泥流是水和火山岩碎片快速流动的混合物，造成了历史上一些最严重的火山灾害。火山泥流有多种类型和过程，主要与水和岩石颗粒的相对体积有关。灾害预测所需的现有模型可以很好地处理极端的火山泥流行为（洪水和雪崩），但需要新的模型来覆盖这些复杂现象的广泛中间地带，并包括火山泥流的下游演变以及对位于潜在火山泥流路径上的社区和基础设施的危害的影响。火山泥流可以由松散的火山沉积物上的强降雨，爆炸性喷发的物质与水或冰的混合，或由山顶火山口湖的爆发引发。大多数火山泥流几乎没有预警信号，因此基本上是不可预测的。这项研究利用了一个几乎独特的情况，即新西兰鲁阿佩胡火山新填满的火山口湖预计会爆发洪水，并将与圣海伦斯火山进行比较。这项研究由岩石学和地球化学以及EPSCoR项目共同资助，美国和新西兰的科学家、学生和应急管理人员将参与制作一种用户友好的灾害预测工具。科学的方法包括将现场数据与火山泥流过程的计算建模相结合。该团队将开发方法，用数学方法描述火山泥流复杂的物理过程，以及它们从源头流出时特征演变的方式。这个新模型将是第一个详细处理泥流就位期间沉积物和水的增加和损失的模型，从而占据了现有质量流模型无法很好地处理的生态位。泥沙夹带过程已被发现是导致流量增加许多倍的原因，因此对于了解下游危害的程度显然很重要。在应用于更广泛的火山和火山泥流触发机制之前，对两座火山的实地研究将为该模型提供验证。通过将最终产品包装成一个用户友好的危害预测工具，它旨在弥合火山泥流研究人员和可能直接受益于该项目的社区之间的差距。