Computational modeling of volcanic eruptions and their seismic and infrasound radiation

类似于1980年圣海伦斯火山爆发的火山爆发可以在安全距离外通过地震仪和麦克风进行监测，地震仪可以测量地面的震动，麦克风可以测量大气中的声波。这个项目的总体目标是研究震动、声波、火山内部发生的情况和喷发羽流之间的联系，以及为什么会发生爆炸性喷发。一种可能是岩浆通道被堵塞，导致压力积聚，最终破坏堵塞并导致火山喷发。项目团队将开发计算机模拟，跟踪岩浆穿过火山管道（在某些情况下，必须突破阻塞），变成碎片，并排放到大气中。这些模拟可以预测火山喷发产生的声波和地面震动。这些模型的预测结果将与2013-2014年厄瓜多尔通古拉瓦火山爆发的数据进行比较，这可能是有记录以来最强大的爆发。这项研究将与厄瓜多尔地质研究所合作进行，该研究所将提供有关火山喷发的数据和专业知识。该项目将为两到三名博士生和几名本科生提供培训，该团队开发的模拟火山喷发的所有计算机程序将与其他科学家免费共享。该项目开发了火山喷发的地震和次声辐射模型。目标是利用地震和次声数据来量化碎裂的深度、爆发时与塞子破裂相关的力、大规模喷发速率和总喷发质量，以及固体地球和大气之间的垂直动量交换。这有助于了解火山喷发的基本过程（例如，在什么条件下形成塞子以及导致塞子破裂的原因），并为喷发羽流建模提供输入。该项目建立在以前nsf支持的项目团队的工作基础上，该项目团队提出了从非稳态管道流动模型计算合成地震记录的理论和工作流程。该项目团队正在继续开发一个开源代码，该代码将管道流与可压缩大气相结合，从而还可以预测次声辐射以及喷发射流和羽流的流动结构。这个整体的建模框架将用于了解过程的一般研究，以及研究地震和次声数据可用的实际喷发。对于后者，项目团队与厄瓜多尔地质研究所合作，模拟了2013-2014年有详细记录的通古拉瓦火山喷发。该项目的另一个组成部分是对地震喷发震颤（~1-10赫兹波段的非相干波）的研究，这是爆炸性喷发的普遍特征，在某些情况下与羽流高度相关。项目团队将探索火山喷发震颤的多种假设，包括破碎上方的湍流和粒子壁相互作用，以及具有可变粘度和其他性质的岩浆通过破碎深度时破碎过程的不稳定性。最后，项目团队正在将水（包括相变）纳入他们的多相建模代码中，使他们能够研究岩浆与地下水和海水的相互作用，包括海底喷发。开源代码和建模工作流程将提供给社区，供火山观测站和其他研究人员使用。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。

Explosive volcanic eruptions similar to the 1980 Mount Saint Helens eruption can be monitored from a safe distance using seismometers, which measure shaking of the ground, and microphones, which measure sound waves in the atmosphere. The overall goal of this project is to develop connections between shaking, sound waves, what’s going on inside a volcano and its eruption plume, and why explosive eruptions occur. One possibility is that the magma conduit gets blocked, leading to pressure build-up which eventually destroys the blockage and causes an eruption. The project team will develop computer simulations that track magma as it travels through the volcanic conduit (in some cases, having to break through blockages), becomes fragmented, and is discharged into the atmosphere. These simulations can predict sound waves and ground shaking generated by the eruption. Predictions from the models will be compared with data from the 2013-2014 explosive eruptions of Tungurahua volcano in Ecuador, which are probably the most powerful explosive eruptions ever recorded. This research will be done in partnership with the Instituto Geofisico in Ecuador, who will be providing data and expert knowledge of the eruptions. The project will provide training for two to three PhD students and several undergraduates, and all of the computer programs the team develops to simulate the eruptions will be freely shared with other scientists.This project develops models of seismic and infrasound radiation from vulcanian eruptions. The goal is to use seismic and infrasound data to quantify the depth of fragmentation, the forces associated with plug rupture at the onset of eruptions, the mass eruption rate and total erupted mass, and the vertical momentum exchange between the solid Earth and atmosphere. These are useful to understand fundamental processes involved in vulcanian eruptions (e.g., under what conditions does a plug form and what causes it to rupture) and to provide inputs to eruption plume modeling. The project builds on previous NSF-supported work by the project team that produced the theory and workflow to compute synthetic seismograms from unsteady conduit flow models. The project team is continuing work on an open-source code that couples conduit flow to a compressible atmosphere, thereby also providing predictions of infrasound radiation and the flow structure of the eruptive jet and plume. This overall modeling framework will be used for generic studies to understand processes as well as to study actual eruptions for which seismic and infrasound data are available. For the latter, the project team has partnered with the Insituto Geofisico, Ecuador, to model the well-recorded 2013-2014 eruption of Tungurahua volcano. An additional component of the project is a study of seismic eruption tremor (incoherent waves in the ~1-10 Hz band), a ubiquitous characteristic of explosive eruptions that in some cases is correlated with plume height. The project team will explore multiple hypotheses for eruption tremor, including turbulence and particle-wall interactions above fragmentation, as well as unsteadiness of the fragmentation process as magma with variable viscosity and other properties passes through the fragmentation depth. Finally, the project team is incorporating water (including phase changes) into their multiphase modeling code, giving them the ability to study the interaction of magma with groundwater and seawater, including submarine eruptions. The open-source codes and modeling workflows will be provided to the community for use by volcano observatories and other researchers.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.