ニイラゴンゴ・ニアムラギラ火山の火山性地震と微動について

抄録

The volcanic earthquakes and tremors occurring in the volcanic regions of Nyiragongo and Nyamuragira in the Republic of Zaire are investigated by use of the data from Lwiro (LWI) and the temporary observations carried in 1972 and 1977. The main results obtained in this paper are as follows:
1) The volcanoes Nyiragongo and Nyamuragira are the most active volcano-seismic regions in the Virunga Volcano. The volcanic earthquakes of type B are located only in the Nyamuragira region and their epicenters are distributed along the fissure of which the direction is NNW-SSE. On the other hand, the earthquakes called type A are located in the narrow area of the northern part of Nyiragongo.
2) Judging from the number of the volcanic earthquakes recorded at LWI, the volcano-seismic activity changed at the beginning of 1975.
3) In the case of the Rugarama eruption, 1971, the occurrence of volcanic earthquakes had a close relationship to the magma flow to the surface. The precursory energy decrease of volcanic earthquakes is found to occurr at three months before the eruption.
4) In the regions of Nyiragongo and Nyamuragira, three magma reservoirs are found based on the spatial distribution of predominant frequency of volcanic tremor. The magma reservoir found under the crater Nyamuragira is considered to be persistent. The linear dimension of the reservoir is estimated to be around 2km.