| Project/Area Number |
07041079
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Field Research |
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| Research Institution | Tohoku University |
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Principal Investigator |
HAMAGUCHI Hiroyuki Fac. Sci., Tohoku Univ. Prof., 理学部, 教授 (20004385)
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| Co-Investigator(Kenkyū-buntansha) |
AKUMBI M. C.R.S.N., Zaire, Technician, 技術官
MAVONGA T. C.R.S.N., Zaire, Reseracher, 研究員
WAFULA M. C.R.S.N., Zaire, Reseracher, 研究員
ZANA N. G.R.C., Zaire, Dirctor & Prof., 所長
NISHIMURA Takeshi Fac. Sci., Tohoku Univ., Assoc. Res., 理学部, 助手 (40222187)
MORITA Yuichi Fac. Sci., Tohoku Univ., Assoc. Res., 理学部, 助手 (30220073)
KASAHARA Minoru Fac. Sci., Hokkaido Univ., Assoc. Prof., 理学部, 助教授 (40001846)
ISHII Hiroshi Earthq. Res. Inst., Univ. Tokyo. Prof., 地震研究所, 教授 (30004386)
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| Project Period (FY) |
1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1995: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Keywords | Africa / Rift System / Volcanic Activity / Eruption / Hotspot / Earth's Structure / Nyiragongo / Earthquake |
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| Research Abstract |
Although there are many hotspot volcanoes in the African plate, the Nyiragongo volcano in the eastern Zaire presents the highest potential threat to the local habitants. This potential has been recently much enhanced by (a) the starting volcanic eruptions at Nyiragongo on June 23,1994, and (b) the abnormal increasing population of about 1 million refugee fleeing from Rwanda on the middle of July, 1994. We have installed the seismo-volcanic monitoring systems around the volcano. Based on the instrumental observations, we showed that the seismic swarm activities have been high stages in the period between 1994 and 1996 and that they were located at the NE,NW and SE parts of Nyiragongo volcano. Recently, the number of felt earthquakes increased gradually around the volcanic area. We have continued to monitor the change of lava-lake level in the crater of Nyiragongo since August, 1994. We showed that the level of lava lake has ascending with a constant rate of 28 cm/day until July 1995 and that the supply rate of basaltic magma was estimated to be 2.2x10^5m^3/day. This ascend was stopped around October, 1995. The color of lake water in Kivulake changed at the northern part of the lake since February, 1996, which suggests the existence of submarine volcanic activity on the lake bottom. The above mentioned our observations clearly show that the present volcanic activity of Nyiragongo is still very active stages in all aspects.
We also investigated the heterogeneity and anisotropy in the inner core. The heterogeneity in the core was examined by using differential travel times of PKP(BC)-PKP(DF). The geographical pattern of the travel time residuals was found to be a manifestation of degree one heterogeneity in the outermost about 500 km of the inner core. Spherical harmonics analysis showed that the P velocities were fast in the region from 43ﾟ E to 177ﾟ E and slow in the region from 183ﾟ W to 43ﾟ E.Geophysical implications of this pattern are briefly discussed.
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