Evidence for near-source nonlinear propagation of volcano infrasound from Strombolian explosions at Yasur Volcano, Vanuatu
Evidence for near-source nonlinear propagation of volcano infrasound from Strombolian explosions at Yasur Volcano, Vanuatu
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DOI：
10.1007/s00445-022-01552-w
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发表时间：
2022-03
影响因子：
3.5
通讯作者：
S. Maher;R. Matoza;A. Jolly;C. de Groot-Hedlin;K. Gee;D. Fee;A. Iezzi
中科院分区：
文献类型：
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作者：
S. Maher;R. Matoza;A. Jolly;C. de Groot-Hedlin;K. Gee;D. Fee;A. Iezzi
火山喷发源参数可以从次声频率（< 20 Hz）处占主导地位的声压记录中估计，但不确定性可能很高，部分原因是对传播动力学知之甚少。通常假设火山次声的线性声传播，但非线性过程，如波变陡可能会扭曲波形和模糊记录波形中的源过程。在这里，我们使用一个以前开发的频域非线性指标，量化频谱变化，由于非线性传播主要是在80个信号，从爆炸在亚苏尔火山，瓦努阿图。我们发现，在200-400 m范围内，在3-9 Hz频带内，振幅为几百Pa的信号的频谱能量转移为10 −3dB/m。非线性光谱特征的清晰度随波形幅度的增加而增加，表明对于更大的源压力，非线性变化更强。我们观察到类似的结果，在应用中产生的合成通过有限差分波场模拟的非线性传播，虽然模型的局限性复杂的直接比较的意见。我们的研究结果为非线性传播提供了定量的证据，证实了以前的解释的基础上的非对称波形的定性观察。
Volcanic eruption source parameters may be estimated from acoustic pressure recordings dominant at infrasonic frequencies (< 20 Hz), yet uncertainties may be high due in part to poorly understood propagation dynamics. Linear acoustic propagation of volcano infrasound is commonly assumed, but nonlinear processes such as wave steepening may distort waveforms and obscure the sourcing process in recorded waveforms. Here we use a previously developed frequency-domain nonlinearity indicator to quantify spectral changes due to nonlinear propagation primarily in 80 signals from explosions at Yasur Volcano, Vanuatu. We find evidence for10−3dB/m spectral energy transfer in the band 3–9 Hz for signals with amplitude on the order of several hundred Pa at 200–400 m range. The clarity of the nonlinear spectral signature increases with waveform amplitude, suggesting stronger nonlinear changes for greater source pressures. We observe similar results in application to synthetics generated through finite-difference wavefield simulations of nonlinear propagation, although limitations of the model complicate direct comparison to the observations. Our results provide quantitative evidence for nonlinear propagation that confirms previous interpretations made on the basis of qualitative observations of asymmetric waveforms.