Understanding cyclic seismicity and ground deformation patterns at volcanoes: Intriguing lessons from Tungurahua volcano, Ecuador
Understanding cyclic seismicity and ground deformation patterns at volcanoes: Intriguing lessons from Tungurahua volcano, Ecuador
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DOI：
10.1016/j.epsl.2017.10.050
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发表时间：
2018-01
影响因子：
5.3
通讯作者：
J. Neuberg;A. Collinson;P. Mothes;M. Ruiz;Santiago Aguaiza
中科院分区：
文献类型：
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作者：
J. Neuberg;A. Collinson;P. Mothes;M. Ruiz;Santiago Aguaiza
在世界各地的许多火山上观测到周期性地震活动和地面变形模式，其中地震群和火山侧翼的倾斜为评估火山活动状态提供了敏感的工具。活火山的地面变形通常被解释为岩浆储层的压力变化，而倾斜则被简单地解释为岩浆储层的膨胀和收缩。然而，厄瓜多尔通古拉瓦火山山顶地区的仪器记录的倾斜数据，在几个场合显示了一个有趣的和意想不到的行为：在火山爆发之前，当系统的增压预计，倾斜信号显著下降，因此表明减压。与此同时，地震活动急剧增加。设想这样的模式可能具有预测通古拉瓦火山爆发的潜力，我们使用数值模拟和再现在空间和时间上观察到的倾斜模式。我们证明倾斜信号可以更容易地解释为由粘性流动阻力引起的剪切应力引起的，而不是由岩浆管道系统的增压引起的。总的来说，我们的数值模型证明，如果岩浆剪切粘度和上升速率足够高，所产生的剪切应力足以产生在通古拉瓦观测到的倾斜信号。此外，我们通过剪切应力划分解决了倾斜和地震活动性的相互依存关系，并提出倾斜和地震活动性的联合解释可以为硅火山的喷发潜力提供新的线索。
Cyclic seismicity and ground deformation patterns are observed on many volcanoes worldwide where seismic swarms and the tilt of the volcanic flanks provide sensitive tools to assess the state of volcanic activity. Ground deformation at active volcanoes is often interpreted as pressure changes in a magmatic reservoir, and tilt is simply translated accordingly into inflation and deflation of such a reservoir. Tilt data recorded by an instrument in the summit area of Tungurahua volcano in Ecuador, however, show an intriguing and unexpected behaviour on several occasions: prior to a Vulcanian explosion when apressurisationof the system would be expected, the tilt signal declines significantly, hence indicatingdepressurisation. At the same time, seismicity increases drastically. Envisaging that such a pattern could carry the potential to forecast Vulcanian explosions on Tungurahua, we use numerical modelling and reproduce the observed tilt patterns in both space and time. We demonstrate that the tilt signal can be more easily explained as caused by shear stress due to viscous flow resistance, rather than by pressurisation of the magmatic plumbing system. In general, our numerical models prove that if magma shear viscosity and ascent rate are high enough, the resulting shear stress is sufficient to generate a tilt signal as observed on Tungurahua. Furthermore, we address the interdependence of tilt and seismicity through shear stress partitioning and suggest that a joint interpretation of tilt and seismicity can shed new light on the eruption potential of silicic volcanoes.