Coupling Between Magmatic Degassing and Volcanic Tremor in Basaltic Volcanism
Coupling Between Magmatic Degassing and Volcanic Tremor in Basaltic Volcanism
复制标题
玄武岩火山活动中岩浆脱气与火山震颤的耦合
DOI：
10.3389/feart.2018.00157
复制
发表时间：
2018
影响因子：
2.9
通讯作者：
C. Oppenheimer
中科院分区：
文献类型：
--
作者：
G. Salerno;M. Burton;G. Di Grazia;T. Caltabiano;C. Oppenheimer
岩浆脱气，通常以二氧化硫通量来衡量，在控制火山喷发方式方面起着关键作用，并且是火山观测站用于评估火山动荡以及探测喷发前兆的关键参数之一。火山颤动，即一定频率范围内地震能量释放的综合振幅，也是火山监测的一个关键参数。通过在动荡期或喷发期经常（但不总是）观测到的信号之间的相关性，推断出了火山脱气和颤动之间存在联系。然而，数据往往不明确，我们对将脱气与颤动联系起来的物理过程的理解仍在不断发展。通过研究脱气与颤动之间的长期关系，关注颤动的频率依赖性以及被动脱气行为，可以对脱气 - 颤动耦合有新的认识。在这项研究中，我们研究了埃特纳火山的长期二氧化硫排放率和火山颤动如何追踪喷发动态的快速变化。在平静期和喷发期都对二氧化硫通量和颤动之间的相关性进行了探究，在大约两年的时间里，在长、短时间尺度（<<1天）上对这两个参数进行了比较。我们的分析表明，在大约一个月的时间尺度上，二氧化硫的被动脱气和颤动往往具有良好的相关性，但在较短的时间尺度上这些相关性消失。这反映了被动脱气和颤动之间的耦合过程，该过程是由气体通过渗透性岩浆的流动以及岩浆在管道内的对流共同作用产生的。短期相关性消失是因为连续脱气过程中的变化与总体脱气率相比相对较小，并且低于测量噪声。在喷发期，脱气和颤动之间观察到很强的相关性，颤动中高频信号的贡献更大，这受喷发方式的控制。这些观察结果表明，在单一喷发期，颤动源主要是由喷发柱通过次声波与地面之间的耦合所主导，而不是管道过程。我们的研究结果证明了高质量长期观测的重要性，并为活火山中脱气和火山颤动耦合的物理机制提供了新的见解。
Magmatic degassing, typically measured as SO2 flux, plays a key role in controlling volcanic eruption style and is one of the key parameters used by volcano observatories to assess volcanic unrest and detect eruption precursors. Volcanic tremor, the integrated amplitude of seismic energy release over a range of frequencies, is also a key parameter in volcano monitoring. A connection between volcanic degassing and tremor has been inferred through correlations between the signals which are often, but not always, observed during periods of unrest or eruption. However, data are often equivocal and our understanding of the physical processes, which couple degassing with tremor are still evolving. New insights into degassing-tremor coupling can be made by investigation of the long-term relationship between degassing and tremor, focussing on the frequency-dependence of tremor and passive degassing behaviour. In this study, we examine how long-term SO2 emission rates and volcanic tremor on Mt. Etna, track rapid variability in eruptive dynamics. Correlations between SO2 flux and tremor are explored in both quiescent and eruptive periods, comparing the two parameters at both long and short time-scales (<< 1 day) for ~2 years. Our analysis reveals that over month-long timescales passive degassing of SO2 and tremor tend to be well-correlated, but these correlations are lost over shorter timescales. This reflects a coupling process between passive degassing and tremor, produced by a combination of gas flow through permeable magma and the convective flow of magma within the conduit. Short-term correlations are lost because variations in the continuous degassing process are relatively small compared with the overall degassing rate and fall below measurement noise..During eruptive periods strong correlations are observed between degassing and tremor, with a greater contribution of higher frequency signal in tremor, controlled by eruptive style. These observations suggest that in sin-eruptive periods the tremor source is dominated by the coupling between the eruption column and the ground through infrasonic waves, rather than conduit processes. Our results demonstrate the importance of high quality long-term observations and offer new insights into the physical mechanisms which couple degassing and volcanic tremor at active volcanoes.
影响因子：
2.9
作者：
Beckett F
通讯作者：
Beckett F
影响因子：
--
作者：
P. Wallace;M. Edmonds
通讯作者：
P. Wallace;M. Edmonds