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SIMULTANEOUS ANALYSES OF SEISMIC AND ACOUSTIC SIGNALS ASSOCIATED WITH VOLCANIC ERUPTIONS FOR UNDERSTANDING ERUPTION DYNAMICS

同步分析与火山喷发相关的地震和声学信号，以了解喷发动力学

基本信息

批准号：
18540416
负责人：
OHMINATO Takao
金额：
$ 1.12万
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：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18540416/
关键词：
volcanoes earthquakes acoustic volcanic signals volcanic eruptions numerical simulation of waveforms 空気振動

项目摘要

The goal of this research is developing a new analysis tool of the seismic and acoustic signals accompanying a volcanic eruption, to understand the eruption dynamics. Seismic signals reflect the state of dynamics in the volcanic conduit, while acoustic signals reflect injection rates of hot volcanic material injected into the atmosphere. Each signal has been separately analyzed by various researchers. In this research, I have developed a tool to analyze both types of signals simultaneously. This research is divided into three parts: 1) to develop an analyses tool for acoustic signals, 2) to combine the newly developed analyses tool of acoustic signals with the pre-existing analyses tool of seismic signals, 3) to apply the newly developed tool to the seismic and acoustic signals associated with Mt. Asama eruptions in 2004.The results of the wave form analyses of both seismic and acoustic signals of Mt. Asama eruptions are summarized as follows. From the seismic signals, amplitudes of the vertical single-forces exerted on the volcanic conduit were estimated. From the analyses of the acoustic signals, changes in the injection rate of hot volcanic material into the atmosphere were estimated. The comparison of the results of the analyses of both types of signals revealed that the amplitude ratio between the two signals vary significantly from eruption to eruption. For example, the eruption in September 1st, 2004 is characterized by strong acoustic signals and weak seismic signals, while the eruption in September 23rd has the opposite character. A model with varying thickness of the cap of the volcanic conduit can explain the observed variation of the amplitude ratio. The cap thickness variation predicted by this model is in good agreement with the observed change in the elevation of the crater bottom which is proportional to the change in the cap thickness.

本研究的目的是开发一种新的分析工具，地震和声波信号伴随着火山喷发，了解喷发动力学。地震信号反映了火山管道中的动力学状态，而声学信号则反映了热火山物质注入大气的注入速度。每个信号都被不同的研究人员单独分析。在这项研究中，我开发了一种工具来同时分析这两种类型的信号。本研究分为三个部分：1）开发声信号分析工具; 2）将新开发的声信号分析工具与已有的地震信号分析工具相结合; 3）将新开发的声信号分析工具应用于与Mt.对浅间火山的地震信号和声波信号进行了波形分析。浅间火山喷发的情况总结如下。根据地震信号，估计了施加在火山管道上的垂直单力的振幅。根据对声学信号的分析，估计了热火山物质注入大气层的速度的变化。两种类型的信号的分析结果的比较表明，两个信号之间的振幅比显着不同的喷发。例如，2004年9月1日的火山喷发具有强声信号和弱地震信号的特征，而9月23日的火山喷发则具有相反的特征。一个模型与不同厚度的火山管道盖可以解释所观察到的变化的振幅比。由该模型预测的帽厚度变化与观察到的火山口底部高程的变化很好地吻合，火山口底部高程的变化与帽厚度的变化成正比。