Collaborative Research: Constraining Volcanic Jet Dynamics with Infrasound Using Numerical and Empirical Models

爆炸性火山喷流产生的喷发柱通常形成漂浮的灰云，并可能完全或部分坍塌形成火山碎屑密度流，这是危险的快速移动的热灰和气体横向流动。 这些自然灾害直接威胁到周边社区和全球空中交通。 我们减轻这些风险的能力受到限制，因为我们无法安全地测量火山喷流或监测它们的共同爆发。 次声（频率低于人类听觉的声学信号）提供了一种检测距离火山几米到几千公里的大气振荡的手段。该项目旨在利用这些信号来限制火山喷流的物理特性，并实时测量它们。 这些测量值可用作航空安全灰云预测模型的输入参数，并用于评估特定火山爆发对当地社区造成的危害。此外，这项工作将为数值和实验研究提供火山喷发参数和物理学方面的限制，最近火山喷流的次声记录具有与人造喷流（喷流噪声）产生的声学信号相似的频谱。在过去的60年里，航空声学研究了人造射流的流动特性与产生的声学信号之间的关系。 我们的长期目标是通过确定火山喷发产生的次声信号的基础上，火山喷流的流动特性，扭转这一概念。 这项工作是朝着这一长期目标迈出的第一步。 我们开始建立一个目录的次声喷流噪声观测，以确定特征火山喷流噪声功能，并确定这些功能和已知的喷发参数之间的任何相关性。 这个过程包括使用新的信号处理工具和经验和理论传播建模搜索现有的次声数据库。 然后，我们将使用火山喷流的分析和数值模型，以适应已建立的经验模型的人造喷气噪音火山system.This项目的地球物理学和岩石地球化学计划和实验计划，以刺激竞争力的研究（EPSCoR）的支持。

Explosive volcanic jets produce eruption columns that often form buoyant ash clouds and may fully or partially collapse to form pyroclastic density currents, dangerous fast-moving lateral flows of hot ash and gas. These natural hazards directly threaten surrounding communities and global air traffic. Our ability to mitigate these risks is restricted by our inability to safely measure volcanic jets or monitor them co-eruptively. Infrasound (acoustic signals with frequencies below that of human hearing) provides a means to detect the atmospheric oscillations from volcanoes at distances of meters to thousands of kilometers from the source. This project aims to use these signals to constrain the physics of volcanic jets and measurethem in real-time. These measurements may be used as input parameters for aviation safety ash-cloud prediction models and toward assessing the hazard presented to local communities by a given eruption. Additionally, this work will provide constraints on eruptive parameters and physics for numerical and experimental studies.Recent infrasound recordings of volcanic jets have frequency spectra similar to the acoustic signal produced by man-made jets (jet noise). For the past 60 years, aeroacoustics has studied the relationship between the flow properties of man-made jets and the acoustic signal produced. Our long-term objective is to reverse this concept by determining the flow properties of volcanic jets based on the infrasound signal produced by the eruption. This work represents a first step toward this long-term goal. We begin by building a catalog of infrasonic jet noise observations to determine characteristic volcanic jet noise features and determine any correlations between these features and known eruptive parameters. This process includes searching existing infrasound databases using new signal processing tools and empirical and theoretical propagation modeling. We will then use analytical and numerical models of volcanic jets to adapt established empirical models of man-made jet noise to volcanic systems.This project is supported by the Geophysics and Petrology & Geochemistry Programs and the Experimental Program to Stimulate Competitive Research (EPSCoR).