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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Simulation and inversion of harmonic infrasound from open-vent volcanoes using an efficient quasi-lD crater model
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Simulation and inversion of harmonic infrasound from open-vent volcanoes using an efficient quasi-lD crater model

机译：利用高效准立用陨石坑模型仿真和谐波次谐波的反演

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摘要

Volcanic activity excites low frequency acoustic waves, termed infrasound, in the atmosphere. Infrasound observations can be used to provide constraints on eruption properties, such as crater geometry and volume flux. At open-vent volcanoes, such as Erebus (Antarctica) and Villarrica (Chile), the infrasound signal is modulated by the crater properties. Eruptive activity at the bottom of the crater, such as unsteady degassing or explosions, can excite the air mass within the crater into resonance leading to infrasound generation with signals possessing clear spectral peaks, termed harmonics. Therefore, the effect of the crater on the infrasound signal, or crater acoustic response, must be accounted for when inverting harmonic infrasound observations for eruption properties at open-vent volcanoes. Here we develop a linearized model of quasi one-dimensional (1D) wave propagation inside volcanic crater coupled with 3D axisymmetric radiation into the atmosphere from the crater, with waves generated by a volumetric flow rate source at the bottom of the crater. We perform simulations for a range of volcanic crater geometries, temperature profiles. gas compositions, and source descriptions to explore the influence of these properties on the infrasound signal. The observed infrasound signal depends on the flow rate source-time function, but interference of up- and down-going waves within the crater selectively amplifies the signal at the resonant frequencies of the crater. The crater resonance model presented here is verified by comparison with an established three-dimensional (3D) infrasound code and is shown to be appropriate for realistic crater geometries when the crater radius is less than approximately one quarter of the acoustic wavelength. The model presented here is more computationally efficient and can be used to invert infrasound observations for a range of properties, such as crater geometry or volumetric flow rate associated with eruptions. We demonstrate the utility of our efficient modeling framework by inverting harmonic infrasound observations for the crater geometry and position of the lava lake at Villarrica volcano. This technique may be used at other open-vent volcanoes to constrain dynamic crater geometry and provide insights about lava lake motions and infrasound producing eruption sources. (C) 2019 Elsevier B.V. All rights reserved.
机译：火山活动激发低频声波，在大气中称为Infrasound。基于对喷发性能的限制，可以使用基于喷发性质的约束，例如火山口几何形状和体积通量。在开放式火山（如Erbus（南极洲）和Villarrica（智利），基于火山口属性调制射击信号。火山口底部的爆发活动，例如不稳定的脱气或爆炸，可以激发火山口内的空气质量，以共振，导致具有透明光谱峰的信号，称为谐波。因此，必须考虑在开放式发光火山上反转谐波性能的谐波基础次出现时，应当考虑火山口对基础信号或火山口声反应的影响。在这里，我们在从火山口耦合到从火山口的3D轴对称辐射到大气中的火山岩喷射器内的准一维（1D）波传播的线性化模型，通过火山口底部的体积流量源产生的波。我们对一系列火山岩地几何形状进行模拟，温度曲线。气体组成，以及探讨这些特性对基础信号的影响的源描述。观察到的基于流量源时间函数取决于流速源时间函数，但是火山口内的上行波的干扰选择性地放大了火山口的谐振频率的信号。这里呈现的火山口谐振模型通过与已建立的三维（3D）Infrasound代码进行比较验证，并且当火山口半径小于声波长度的大约四分之一时，将适合于现实的火山口几何图。这里呈现的模型更加计算地高效，可用于反转基于一系列性质的基础观测，例如与爆发相关的火山口几何形状或体积流速。我们展示了我们有效的建模框架通过反转谐波的基础序列观测，在Villarrica火山的火山岩几何形状和熔岩湖的位置反转。该技术可以在其他开放式发光火山上使用，以限制动态火山口几何形状，并为熔岩湖运动和基础驱动喷发来源提供有关漏洞的见解。 （c）2019 Elsevier B.v.保留所有权利。

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