Time constraints for modeling source dynamics of volcanic explosions at Stromboli
Time constraints for modeling source dynamics of volcanic explosions at Stromboli
复制标题
斯特龙博利火山爆发源动态建模的时间限制
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
M. D. Schiava
中科院分区：
文献类型：
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作者：
M. Ripepe;S. Ciliberto;M. D. Schiava
爆炸源机制，负责斯特龙博利火山活动，分析地震和次声测量与数字处理图像的爆炸事件。与短周期地震信号相关的次声记录证明，高频（>5 Hz）波场是由与大气耦合的震源产生的。地震和次声爆发之间的时间延迟是不稳定的，波动可能反映了岩浆-气体物理性质的变化和/或源在岩浆管道中的迁移。气体射流速度，计算的摄像机图像，和地震和次声开始之间的时间延迟表现出弱的反相关性。在实验室实验中，通过记录气泡在液体中生长、流动和破裂过程中产生的声信号，对泡沫破裂模型进行了检验。观测到的信号与斯特龙博利记录的短周期（>1秒）和宽带（10-1秒）地震信号有很强的相似性。当泡沫破裂时，观察到低频稀疏，气泡开始沿管道沿着上升，然后在液体自由表面处的气泡膜破裂发出可听见的声音。以此类推，我们推断低频地震减压是由岩浆通道中气体的快速膨胀产生的，而高频地震信号和次声则是由岩浆自由面的爆炸产生的。地震、次声和可见光爆炸开始之间的时间差确定爆炸源在海拔600米以上。
The explosive source mechanism, responsible for the volcanic activity of Stromboli, is analyzed by seismic and infrasonic measurements in correlation with digitally processed images of the explosive events. Infrasonic recordings associated with short-period seismic signals give evidence that the high-frequency (>5 Hz) wave field is produced by a seismic source coupled to the atmosphere. The time delay between seismic and infrasonic onsets is not stable and the fluctuations could reflect a change in the magma-gas physical properties and/or a migration of the source in the magma conduit. The gas jet velocity, calculated by videocamera images, and the time delay between seismic and infrasonic onset show a weak inverse correlation. The foam collapse model has been checked in laboratory experiments by recording acoustic signals produced during gas bubbles growth, flow, and burst in a liquid. The observed signals present strong similarities to short-period (>1 s) as well as broadband (10–1 s) seismic signals recorded at Stromboli. Low-frequency rarefaction is observed when the foam collapse occurs and the gas bubble starts to rise up along the pipe, then the bubble film breaking at the liquid free surface emits an audible sound. By analogy, we infer that low-frequency seismic decompression is generated by the rapid expansion of gas in the magma conduit, while high-frequency seismic signal and infrasound are generated by the explosion at the magma free-surface. The time differences between seismic, infrasonic and visible onset of the explosion locate the explosive source at 600 m above sea level.