Collaborative Research: Linking pyroclastic surge dynamics and deposits through integration of field data, multiphase numerical modeling, and experiments

火山爆发释放出的热气体和颗粒流称为火山碎屑潮;这些对人类是致命的，并严重损坏或摧毁建筑物和其他基础设施。 在美国境内，火山碎屑潮是许多地区的潜在危险，如西南部和沿着太平洋西北部的喀斯喀特山脉。了解参数，如速度，压力，温度和颗粒浓度是必要的预测火山碎屑浪涌的危险，并采取缓解措施。对活跃的火山碎屑涌进行测量基本上是不可能的，因为它们是不可预测的，而且会造成极端的条件。 因此，我们必须使用间接的方法：（1）详细研究火山碎屑涌产生的沉积物，这可以在火山平静后进行研究;（2）旨在复制涌的某些方面的实验;（3）流动的计算机建模。 这个项目反复使用这三种方法。这项工作将为预测和减轻火山灾害提供新的见解和工具。 此外，这项工作将由一个多元化的、新成立的多所大学的团队完成，将培养两名新的博士。学生，并将加强学术研究人员与美国地质调查局之间的伙伴关系，其中有主要责任的危害assessment.Controls的发展，当地相在火山碎屑浪涌存款以及更大规模的参数，如近端到远端相的变化，跳动，和损害的潜力知之甚少。 我们将解决以下研究问题：（1）在当地规模（例如，个别露头或一组露头），底形和相与悬移质、推移质通量和局部地形的沉积作用有何关系？ (2)在大尺度上（从近端到远端），沉积作用、地形、初始温度、质量通量和大气夹带对大尺度相分布、跳动距离和损害潜力的作用是什么？拟议的工作包括三个组成部分。(1)详细的实地研究将侧重于两个保存完好的年轻矿床（加州的Ubehebe火山;索诺拉的Crater Elegante），记录岩相、粒度和组分，作为距喷口距离和当地地形环境的函数。(2)实验将测试和扩展一个简单的沙丘形状参数之间的关系，可测量的领域，推移质通量，和悬移质沉降通量。(3)多相数值模拟将使用自适应网格细化来解决床附近的通量，将改进气体和极细灰（浪涌传输和沉积的关键）之间耦合的数值解，并将使用非结构化网格技术来模拟复杂自然地形上的浪涌传输。 一个新的多相建模工具，从该项目的结果将提供给广大的研究社区。这个奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的知识价值和更广泛的影响审查标准。

Explosive volcanic eruptions unleash flows of hot gases and particles called pyroclastic surges; these are deadly to humans and severely damage or destroy buildings and other infrastructure. Within the United States, pyroclastic surges are a potential hazard in many areas such as the Southwest and along the Cascade Range of the Pacific Northwest. Understanding parameters such as speed, pressure, temperature, and particle concentration is necessary to predict pyroclastic surge hazards and to take mitigative measures. Measurements of active pyroclastic surges are essentially impossible because of their unpredictability and the extreme conditions they create. As a result, we must use indirect methods: (1) detailed study of the deposits that were produced by pyroclastic surges, which can be studied after a volcano has gone quiet; (2) experiments aimed at replicating some aspects of the surges; and (3) computer modeling of the flows. This project uses these three methods iteratively. The work will provide new insights and tools to use in forecasting and mitigating volcanic hazards. In addition, the work will be done by a diverse, newly-formed multi-university team, will train two new Ph.D. students, and will strengthen partnership between academic researchers with the U.S. Geological Survey, which has primary responsibility for hazard assessment.Controls on the development of local facies in pyroclastic surge deposits as well as larger-scale parameters such as proximal-to-distal facies variations, runout, and damage potential are poorly understood. We will address the following research questions: (1) At the local scale (e.g., individual outcrop or group of outcrops), what are the relationships of bed forms and facies to sedimentation from suspended load, bed load flux, and local topography? (2) At the large scale (proximal to distal), what are the roles of sedimentation, topography, initial temperature, mass flux, and atmospheric entrainment on large-scale facies distribution, runout distance, and damage potential? The proposed work includes three components. (1) Detailed field studies will focus on two well-preserved, young deposits (Ubehebe volcano, California; Crater Elegante, Sonora), with documentation of facies, grainsize, and componentry as functions of distance from vent and local topographic setting. (2) Experiments will test and extend a simple relationship between dune-form parameters measurable in the field, bed load flux, and suspended load sedimentation flux. (3) Multiphase numerical modeling will use adaptive mesh refinement to resolve fluxes near the bed, will improve the numerical solution of coupling between gas and very fine ash (key for surge transport and deposition), and will use unstructured mesh technology to model surge transport over complex natural terrains. A new multiphase modeling tool that results from the project will be available for the research community at large.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.