学会誌「自然災害科学」

2000年有珠山噴火の地殻変動と噴火活動について

Crustal Deformation and Eruptic Activities of Mt. Usu in 2000

森 済*・宇井 忠英*

Hitoshi Y. MORI* and Tadahide UI*

Abstract

Mt. Usu erupted on March 31, 2000 after c.a. 20 years dormancy. Precursory earthquakes started on March 27. Precursory deformation was detected by GPS network surrounding Mt. Usu, conducted by Geographical Survey Institute, since March 28. Institute of Seismology and Volcanology of Hokkaido University made angle and distance measurements and GPS observations, since March 29. As the results of those observations, the center of preeruptive inflational deformations was located at the western part of the summit of Mt. Usu. On the contrary, eruptions of this activity took places at the western foot and at the northwestern foot of Mt. Usu. The ejecta of the first two eruptions include some juvenile fragments which chemical compositions are slightly different from those of the 1944 and the 1977-1978 eruptions. After the first eruption on March 31, the center of uplift was situated at the western foot of Mt. Usu and the deformations on the summit of the volcano stopped. The western foot inflation has been decaying to the end of July and stopped.

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