Switching from seismic to seismo-acoustic harmonic tremor at a transition of eruptive activity during the Shinmoe-dake 2011 eruption
Switching from seismic to seismo-acoustic harmonic tremor at a transition of eruptive activity during the Shinmoe-dake 2011 eruption
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DOI：
10.5047/eps.2013.05.003
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发表时间：
2013-01-01
影响因子：
3
通讯作者：
Yokoo, Akihiko
中科院分区：
文献类型：
--
作者：
Ichihara, Mie;Lyons, John J.;Yokoo, Akihiko
本文报道了2011年日本九州新门大阁火山喷发期间观测到的一系列谐和地震。主要喷发活动始于柱下喷发，其次是熔岩喷出。在喷发的最后阶段，以地震波的形式观察到了简谐震动。在这一阶段观测到的震颤具有不清楚和波动的简谐模式。然而，在大气层中，观察到了许多表明表面发生小爆炸的脉冲声波。当喷流停止、爆炸除气开始时，空气和地震资料中均可观察到声波形式的简谐振动，简谐振型变得更加清晰和稳定。这种简谐震动性质的转变与火山口中堆积的熔岩的快速放空相吻合。根据这些观测和再现了波场特征的实验室实验，我们得出结论：新墨寺的简谐震动序列是由逐渐凝固的熔岩中的气体流经通道而产生的。将我们的结果与在其他火山观察到的少数类似转变的情况进行比较，我们预计这种转变表明火山口的岩浆流变学和排气条件发生了变化，因此也表明了喷发活动的变化。
This paper reports a sequence of harmonic tremor observed during the 2011 eruption of Shinmoe-dake volcano, Kyushu, Japan. The main eruptive activity started with subplinian eruptions, followed by lava effusion. Harmonic tremor was observed as seismic waves during the final stage of the effusive eruption. The tremor observed at this stage had unclear and fluctuating harmonic modes. In the atmosphere, however, many impulsive acoustic waves indicating small surface explosions were observed. When effusion stopped and explosive degassing began, harmonic tremor was observed as acoustic waves in the air and in the seismic data, and the harmonic modes became clearer and more stable. This transition in the character of the harmonic tremor coincided with rapid deflation of the lava that had accumulated in the crater. Based on these observations, and laboratory experiments reproducing the features of the wave fields, it is concluded that the harmonic tremor sequence at Shinmoe-dake was generated by gas flowing through channels in the gradually solidifying lava. Comparing our results with the few cases of similar transition observed at other volcanoes, we expect that the transition indicates changes in magma rheology and degassing conditions in the crater, and therefore of changes in eruptive activity.