Research for internal state of a volcanic conduit based on volcanic tremors, long-period earthquakes, and infrasonic signals

本研究的目的是建立一个新的方法，估计喷发风格的变化有关的振荡数据和内部状态的一个浅部的管道。在2011年的新萌岳火山活动早期，相继发生了亚普林尼式喷发、岩浆喷发和火山喷发等各种活动。我们成功地获得了多项数据，如宽带地震图，倾斜运动和次声信号，在这三个不同的喷发风格，在山顶火山口附近。在火山喷发阶段，几乎所有火山喷发之前都有梯形暴胀，然后是各种时间序列的倾斜运动，在频繁的火山喷发中变得越来越复杂。尽管前面的通货膨胀的复杂的时间序列，我们已经发现前面的持续时间与过去的时间之间的明确的线性关系。这些观察结果可以一致地解释的基础上的假设，火山喷发是由一个灾难性的破裂最强的封闭，固体岩浆框架的导管由于岩浆脱气超压，从岩浆的脱气下降指数随时间的推移。据报道，在Shinmoe-dake喷发活动期间，仅地震谐波震颤和地震声学谐波震颤之间发生了切换。在实验室实验中模拟开关。在较低的流体刚度，一个稳定的，开放的管道产生的实验装置内产生的谐波信号被有效地传输到大气中。我们建立了一种简单的方法来区分次声信号和风噪声，表明它不仅有效地检测主要的喷发，而且还可以检测到产生弱次声的轻微活动，这些次声在波迹中几乎不可见。

The purpose of this research is estimation of eruption style variation establishing a new method relating to oscillation data and an internal state of a shallow part of a conduit. During the early period of volcanic activity at the Shinmoe-dake volcano in 2011, various kinds of activities, such as sub-Plinian eruptions, a magma effusion, and Vulcanian eruptions, occurred sequentially. We succeeded in obtaining multi-items data, such as broadband seismograms, tilt motions, and infrasonic signals, nearby the summit crater during these three different eruption styles. In the Vulcanian stage, almost all Vulcanian eruptions were preceded by trapezoidal inflations followed by various time sequences of tilt motions, which became increasingly more complicated throughout the frequent Vulcanian eruptions. In spite of the complicated time sequences of the preceding inflations, we have found clear linearity between the preceding duration versus elapsed time. These observations can be consistently explained based on the assumption that a Vulcanian eruption is induced by a catastrophic rupture of the strongest closed, solid magma frame in a conduit due to magma degassing overpressure, and the degassing from the magma declines exponentially with time. Switching between seismic-only harmonic tremor and seism-acoustic harmonic tremor has been reported during Shinmoe-dake eruptionactivity. Switching was simulated in a laboratory experiment. At lower fluid stiffness, a stable, open conduit was produced, and the harmonic signals generated within the experimental apparatus were efficiently transmitted into the atmosphere. We established a simple method to distinguish infrasonic signals from wind noise, demonstrating that it effectively detects not only main eruptions, but also minor activity generating weakinfrasound hardly visible in the wave traces.