2005 Fiscal Year Final Research Report Summary
Systematic understanding of magmatic hydrothermal system and reexamination of deep magma energy extraction
| Project/Area Number |
14205152
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
資源開発工学
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
EHARA Sachio Kyushu University, Faculty of Engineering, Professor, 工学研究院, 教授 (10002346)
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| Co-Investigator(Kenkyū-buntansha) |
ITOI Ryuichi Kyushu University, Faculty of Engineering, Professor, 工学研究院, 教授 (50108768)
FUJIMITSU Yasuhiro Kyushu University, Faculty of Engineering, Associate Professor, 工学研究院, 助教授 (10264095)
NISHIJIMA Jun Kyushu University, Faculty of Engineering, Research Associate, 工学研究院, 助手 (40315114)
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| Project Period (FY) |
2002 – 2005
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| Keywords | volcano energy / geothermal energy / heat extraction / volcanic eruption / volcano / Kuju volcano / monitoring / underground structure |
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| Research Abstract |
Geophysical monitoring system was installed in order to clarify the physical changes after the 1995 phreatic eruption of Kuju volcano, central Kyushu, Japan. The observational results were summarized as follows based on the data base which is consisted of thermal, geomagnetic, seismic, and gravity data.
(1)Changes in surface temperature and magnetization of the volcanic body show the quick and continuous cooling of the volcanic body after the 1995 phreatic eruption.
(2)Decrease in gravity at the central part of the volcano and decrease in steam discharge rate show that the quick and continuous cooling of the volcano was caused by the cold meteoric water recharge to the central part of the volcano. Such cold water recharge was induced by the sudden decrease in pressure of the volcanic geothermal reservoir accompanying with the phreatic eruption.
(3)The above quick and continuous cooling of the volcano was well simulated numerically. The numerical model is a three dimensional and transient model.
(4)The depths of volcanic earthquakes became deeper after the 1995 phreatic eruption. The physical mechanism of deepening of the hypocenters was interpreted in terms of the underground temperature decrease after the 1995 phreatic eruption.
(5)A numerical simulation code which includes the detailed degassing process accompanying with the cooling of magma was developed. The magmatic water discharge rate several tens thousands of years after the commencement of the magma cooling was estimated at several tens kg/sec which is similar to the present magmatic water discharge rate from Kuju volcano.
The present thermal structure beneath Kuju volcano was clarified based on the geophysical observations and numerical modeling. The thermal process after the 1995 phreatic eruption of Kuju volcano was similar to the geothermal fluid production without reinjection. This result implies a possible option of volcano energy utilization at Kuju volcano.
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