RAPID: Lethal pyroclastic density current (PDC) generation and transport at Fuego volcano

该快速研究响应（Rapid）奖将用于更好地了解2018年6月3日危地马拉富埃戈火山（Fuego）的致命喷发，特别是导致死亡的火山碎屑密度流（PDCs）。这些PDCs是如何开始的，是什么导致它们走得那么远，以及它们在未来可能形成的条件是什么，这些都是人们知之甚少的问题。通过观察pdc矿床，绘制它们的地图，研究它们在野外的地层学，分析化学、岩石学和物理特征（密度和囊状结构，粒度分布等），并通过使用数值模型来了解它们的流动动力学，该团队希望能够了解pdc物质的来源，以及它是如何破碎和运输的。他们还将研究喷发前和喷发期间的地球物理和地球化学监测数据，特别是来自当地地震网络和卫星遥感数据的数据，以表征喷发的其他方面（喷发强度和持续时间），并将PDC信息放在这一背景下。这些知识将提高我们对这种pdc形成的理解，特别是在像Fuego这样的玄武岩火山，并且可能与世界各地和美国的许多其他类似火山有关。RAPID项目将支持实地测绘、地层和相关联确定、基于无人机的沉积物和潜在源区摄影测量，以及PDC和airfall tephra沉积物的样本收集。对野外采集的样品进行实验室分析的目的是表征PDCs和tephra组分的粒度分布、形状、密度和囊泡性，以及地球化学（主要和微量元素分析）、岩石学和微结构特征。现场和实验室工作将根据位置、体积和持续时间推断出源过程（例如柱状与上斜坡沉积物崩塌）。通过VolcFlow和Titan2D对实际地形地形（高分辨率dem）上PDCs的传播进行数值模拟，结合沉积测绘和体积估算，以及流体起爆和传播的时间和持续时间等地球物理数据，寻找最佳拟合模型参数，推断流体动力学（如速度、质量流量、脉冲体积划分等）。这项研究将与危地马拉火山监测机构insvumeh（国家火山、火山、气象和水文研究所）密切合作进行，研究的结论将为insvumeh监测和预测未来类似事件的努力以及在危险评估过程中可能使用的类似模型提供大量资料。研究结果也将有助于我们了解世界上其他类似玄武岩火山的喷发过程（及其沉积物），特别是块状和火山灰流型pdc的产生和相关沉积物，以及与之相关的危害。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This Rapid Research Response (RAPID) award will be used to better understand the deadly eruption at Fuego volcano (Guatemala) on June 3rd, 2018, and in particular the pyroclastic density currents (PDCs) that caused the fatalities. How those PDCs initiated, what caused them to move that far, and what could be the conditions under which they may form in the future, are all poorly understood issues. By looking at the PDCs deposit, mapping them and study their stratigraphy in the field, analyzing the the chemical, petrological, and physical characteristics (density and vesicularity, grain size distribution, etc.), and by using numerical models to understand their flowing dynamics, this team hopes to be able to tell where the PDCs material came from, and how it was fragmented and transported. They will also look at geophysical and geochemical monitoring data leading up and during the eruption, particularly from the local seismic network and satellite remote sensing data, to characterize other aspects of the eruption as well (eruption intensity and duration) and put the PDC information in that context. This knowledge will improve our understanding of the formation of this kind of PDCs, particularly at basaltic volcanoes like Fuego, and could be relevant to many other similar volcanoes worldwide and in the US.This RAPID award will support fieldwork mapping, stratigraphy and facies associations determination, UAV based photogrammetry of the deposits and potential source area, and sample collection of the PDC and airfall tephra deposits. Laboratory analysis of samples collected in the field will aim to characterize the grain size distribution, shape, density and vesicularity of PDCs and tephra components, as well as geochemical (major and trace element analysis) and petrographic and microtextural characteristics. Field and laboratory work will allow to infer the source process (e. g. column vs. upper slope deposits collapse) in terms of location, volume and duration. Numerical modeling (VolcFlow and Titan2D) of the PDCs propagation over realistic terrain topography (high resolution DEMs), constrained by deposit mapping and volume estimations, and the geophysical data on timing and duration on flow initiation and propagation will be conducted to find the best fit model parameters and infer the flow dynamics (e. g. velocity, mass flow rate, volume partition in pulses, etc.). The research will be conducted in close collaboration with Guatemalan volcano monitoring agency INSIVUMEH (Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia) and the study's conclusions will be highly informative to INSIVUMEH's efforts to monitor and forecast similar events in the future, and the potential use of similar models to be incorporated in the hazard assessment process. The results will also be relevant to our understanding of eruptive processes (and their deposits) at other similar basaltic volcanoes worldwide, in particular the generation of block-and-ash flow type PDCs and associated deposits, and the hazards linked to them.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.