| Budget Amount *help |
¥1,750,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥150,000)
Fiscal Year 2007: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2006: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
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.
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