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

基于火山颤动、长周期地震和次声信号的火山通道内部状态研究

基本信息

批准号：
22540431
负责人：
TAKEO Minoru
金额：
$ 2.75万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2010
资助国家：
日本
起止时间：
2010 至 2012
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-22540431/
关键词：
火山現象数理モデル実験火山地震微動空振

项目摘要

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.

本研究的目的是估计喷发方式的变化，建立一种新的方法，将振荡数据和管道浅部的内部状态联系起来。在2011年新莫代克火山活动的早期，各种活动相继发生，如次普林尼安喷发、岩浆喷发和火山岩喷发。在这三种不同的喷发方式下，我们成功地获得了峰顶火山口附近的宽带地震记录、倾斜运动和次声信号等多项数据。在火山喷发阶段，几乎所有的火山喷发都是在梯形膨胀之前，然后是各种时间序列的倾斜运动，在频繁的火山喷发过程中，这变得越来越复杂。尽管前几次通货膨胀的时间序列复杂，但我们发现前一次通货膨胀持续时间与过去的时间之间存在明显的线性关系。这些观察结果可以基于以下假设来一致地解释：火山喷发是由于岩浆脱气超压导致管道中最强的封闭的固体岩浆框架的灾难性破裂引起的，并且岩浆的脱气随时间呈指数下降。据报道，在新门大地震喷发活动期间，发生了纯地震简谐震颤和地震-声学简谐震颤之间的转换。切换是在实验室实验中模拟的。在较低的流体硬度下，产生了稳定、开放的管道，实验装置内产生的谐波信号可以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，证明了它不仅有效地检测到主要喷发，而且还有效地检测到了在波迹中几乎看不到的次声活动。