Temporal variation in the depth of the magma surface at Aso volcano in 2014?2015
Temporal variation in the depth of the magma surface at Aso volcano in 2014?2015
复制标题
2014~2015年阿苏火山岩浆面深度随时间变化
DOI：
10.1007/s00445-022-01616-x
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发表时间：
2022
影响因子：
3.5
通讯作者：
Kazama Takahito
中科院分区：
文献类型：
--
作者：
Ishii Kyoka;Yokoo Akihiko;Ohkura Takahiro;Kazama Takahito
监测开口火山岩浆表面的深度可以成为推断喷发期间岩浆供应随时间变化的实用工具。我们专注于2014-2015年的阿索火山的岩浆喷发，以估计岩浆表面深度的时间变化，并表明，这需要结合对浅管道几何形状的理解，如果要以有代表性的方式进行。火山爆发从2014年11月开始持续了5个月，并于2015年5月以火山口地面塌陷结束。在喷发期间，我们记录了与频繁的Strombolian爆炸有关的地震声波波形。次声信号显示出几个不同的峰值频率，来自通风口内的声学共振。我们利用地震声信号的时间延迟和次声信号的峰值频率来估计岩浆表面的深度。此外，导管形状的时间变化受到声共振的泛音频率的约束。从喷发开始到2015年1月上旬，岩浆面位于200 m深处，通道为圆柱形管道。后来，在1月和2月之间，岩浆表面上升到120米，管道的形状变成了一个圆锥台，内部张开。这一发现表明，岩浆被注入到浅管道中，并加热和削弱了岩浆表面附近的管道壁。在岩浆喷发停止之前，岩浆表面下降了大约70米。这种岩浆的排出，主要是管道形状的不稳定，导致了火山口底部的坍塌。我们显示了跟踪和评估的深度的岩浆表面和浅管道的几何形状，即使有限的地震声学观测的可能性。
Monitoring the depth of the magma surface at open-vent volcanoes can be a practical tool to infer temporal variations in the magma supply during an eruption. We focus on the magmatic eruption of Aso volcano in 2014–2015 to estimate the temporal change in the depth of the magma surface, and show that this needs to be coupled with an understanding of the shallow conduit geometry if it is to be done in a representative manner. The eruption lasted 5 months from November 2014 and ending with a crater floor collapse in May 2015. During the eruption, we recorded seismo-acoustic waveforms related to frequent Strombolian explosions. The infrasound signals show several distinct peak frequencies derived from acoustic resonance inside the vent. We estimate the depth of the magma surface using the time delay of seismo-acoustic signals and the peak frequency of infrasound signals. In addition, the temporal variation in the shape of the conduit is constrained by the overtone frequency of the acoustic resonance. From the beginning of the eruption to early-January 2015, the magma surface was located at a depth of200 m, and the conduit was a cylindrical pipe. Later, between January and February, the magma surface rose to120 m, and the shape of the conduit changed to a conical frustum flaring inside. This finding indicates that the magma was injected into the shallow conduit and that it heated and weakened the conduit wall near the magma surface. Before the cessation of the magmatic eruption, the magma surface dropped by approximately 70 m. This magma drainage and, primarily, the instability of the conduit shape caused the crater floor to collapse. We show the possibility of tracking and assessing the depth of the magma surface and the shallow conduit geometry even with limited seismo-acoustic observations.