Research for internal state of a volcanic conduit based on volcanic tremors, long-period earthquakes, and infrasonic signals
| Project/Area Number |
22540431
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Solid earth and planetary physics
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| Research Institution | The University of Tokyo |
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Principal Investigator |
TAKEO Minoru 東京大学, 地震研究所, 教授 (00197279)
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| Co-Investigator(Kenkyū-buntansha) |
ICHIHARA Mie 東京大学, 地震研究所, 助教 (00376625)
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| Project Period (FY) |
2010 – 2012
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| Project Status |
Completed (Fiscal Year 2012)
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| Budget Amount *help |
¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000)
Fiscal Year 2012: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2011: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2010: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
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| Keywords | 火山現象 / 数理モデル / 実験 / 火山 / 地震 / 微動 / 空振 |
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| Research Abstract |
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.
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Report
(4 results)
Research Products
(42 results)
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[Presentation] 新燃岳の噴火に伴う傾斜変動2011
Author(s)
前原祐樹, 大湊隆雄, 及川純, 武尾実
Organizer
日本火山学会2011年秋季大会
Place of Presentation
旭川市・大雪クリスタルホール
Year and Date
2011-10-03
Related Report
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