Relationship between infrasound-derived and buoyancy-derived eruption plume volume estimates
Relationship between infrasound-derived and buoyancy-derived eruption plume volume estimates
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次声推导和浮力推导的喷发羽流体积估计之间的关系
DOI：
10.1007/s00445-018-1244-y
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发表时间：
2018
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影响因子：
--
通讯作者：
and Hideki Ueda
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作者：
Taishi Yamada; Hiroshi Aoyama;and Hideki Ueda
利用次声信号估计伴随短暂喷发的离散羽流的体积是可能的。在短暂的（离散的）喷发过程中释放的羽流被模拟为离散的热气流或根热气流。基于离散热上升的一维模型，理论上可以根据最大羽流高度和环境空气密度的垂直分布来估计球形热的初始浮力F0。我们在这里检查次声导出的体积，Vinf，和浮力导出的体积，Vb，来自F0，这取决于重力加速度，和热空气和周围空气之间的密度差之间的关系，以了解如何Vinf与喷发羽流的动力学。我们分析次声数据伴随着火山和潜水喷发在阿索，Shinmoedake，和Lokon-Empung火山估计Vinf，和其他火山。通过对53个事件的检测，我们得到了Vb/Vinf = 16的代表性比值。由于分析的次声信号在开始时共享显著的压力脉冲，因此我们将初始时的羽流体积设为Vinfas，即，像喷气机一样。相反，当它已经夹带了足够量的周围空气并获得F0时，我们将Vbas作为热体积。喷射的体积密度和离散热的比较产生两种制度之间的体积变化率的一个因素为1.8-32，这是一致的比率ofVb/Vinf。我们的研究结果提供了一个有效的指标，以限制喷发卷体使用次声数据与实时监测系统。
Volume estimations for discrete plumes accompanying short-lived eruptions are potentially possible using infrasound signals. Plumes emitted during short-lived (discrete) eruptions have been modeled as discrete thermals or rooted thermals. Based on the one-dimensional model for the rise of a discrete thermal, the initial buoyancy,F0, of a spherical thermal can theoretically be estimated from the maximum plume height and a vertical profile of ambient air density. We here examine the relationship between infrasound-derived volume,Vinf, and the buoyancy-derived volume,Vb, as derived fromF0, which depends on gravity acceleration, and the difference in density between the thermal and surrounding air, to understand howVinfrelates to the dynamics of the eruption plume. We analyze infrasound data accompanying Vulcanian and phreatic eruptions at Aso, Shinmoedake, and Lokon-Empung volcanoes to estimateVinf, and considerVinffrom other volcanoes. We obtain a representative ratio ofVb/Vinfof 16 by examining 53 events. Because the analyzed infrasound signals share a prominent pressure pulse at the onset, we regardVinfas the volume of the plume at initiation, i.e., as a jet. Instead, we considerVbas the thermal volume when it has entrained a sufficient amount of the surrounding air and obtainsF0. Comparison of the bulk density of the jet and the discrete thermal yields a rate of volume change between both regimes by a factor of 1.8–32, which is consistent with the ratio ofVb/Vinf. Our result provides an effective index to constrain erupted plume volume using infrasound data with real-time monitoring systems.