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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Influence of near-source volcano topography on the acoustic wavefield and implication for source modeling
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Influence of near-source volcano topography on the acoustic wavefield and implication for source modeling

机译：近源火山地形对声波场的影响及其对源建模的启示

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In near-source conditions (<5 km), the atmosphere is often assumed to be fully transparent to acoustic waves and to have a small effect on the acoustic wavefield. As a consequence, the propagation of the acoustic waves in the atmosphere near the source is often neglected and waveform is compensated only in amplitude by the inverse of the distance from the source. However, the amplitude distribution at five infrasonic stations deployed around the active craters of the Stromboli volcano, reveals anomalous decay up to -11 dB larger than expected, which cannot be explained in terms of energy loss for geometrical spreading. The distribution of amplitude decay changes for different source positions, suggesting a strong relationship with the source-to-receiver path geometry. By using 2D-FDTD modeling, we show that the anomalous amplitude distribution of the acoustic waves at Stromboli is not necessarily due to the source radiation pattern but it is strongly influenced by the topography of the ground-atmosphere interface. Diffraction and reflection of topography contaminate the acoustic wavefield and have a strong effect in reducing the amplitude and altering the waveform. Our work demonstrates that line-of-sight conditions are quite difficult to be achieved in acoustic experiments and that a detailed knowledge of the topography along the crater-receiver path is necessary whenever infrasound waveforms are used to invert for the source process.
机译：在近源条件下（<5 km），通常认为大气对声波是完全透明的，并且对声波场的影响很小。结果，经常忽略声波在源附近的大气中的传播，并且仅通过与源的距离的倒数来在幅度上补偿波形。但是，在斯特龙博利火山活动火山口周围部署的五个次声站的振幅分布表明，异常衰减比预期大-11 dB，这不能用几何扩展的能量损失来解释。振幅衰减的分布针对不同的源位置而变化，这表明与源到接收器路径的几何形状有很强的关系。通过使用2D-FDTD建模，我们显示了Stromboli处声波的异常振幅分布不一定是源辐射图引起的，而是受地面-大气界面的地形强烈影响的。形貌的衍射和反射会污染声波场，并在减小幅度和改变波形方面具有很强的作用。我们的工作表明，在声学实验中很难达到视线条件，并且每当次声波形用于源过程进行反演时，就必须详细了解火山口-接收器路径的地形。

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