Report on Aira (Japan) — May 1995
Bulletin of the Global Volcanism Network, vol. 20, no. 5 (May 1995)
Managing Editor: Edward Venzke.
Aira (Japan) Explosive ash eruptions continue
Please cite this report as:
Global Volcanism Program, 1995. Report on Aira (Japan). In: Venzke, E. (ed.), Bulletin of the Global Volcanism Network, 20:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199505-282080.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
During April and May, explosive volcanism continued from Minami-dake crater. Throughout April there were 16 eruptions, 13 of them explosive, with the highest ash plume rising 1,800 m above the summit crater on 7 April (table 11). In May there were 36 eruptions, 17 of which were explosive. The highest ash plume of May rose 2,500 m on the 23rd. Monthly ashfall amounts, collected at Kagoshima Meteorological Observatory, 10 km W of Minami-dake crater, were 14 g/m2 and 20 g/m2, respectively for April and May.
|Month||Total Eruptions||Explosive Eruptions||Ash Plume Height||Average daily ashfall (g/m2)||Tremor||EQ's|
|Jan 1995||47||41||2,500+ m||15||--||715|
|Feb 1995||22||12||3,000 m||30||--||424|
|Mar 1995||36||24||4,000 m||9||828||2,041|
|Apr 1995||16||13||1,800 m||14||427||887|
|May 1995||36||17||2,500 m||20||815||1,008|
At a seismic station 2.3 km NE of Minami-dake crater (Station B), 887 earthquakes were recorded in April, and 1,008 in May. Between 1100 and 2200 on 1 April, 147 volcanic earthquakes were registered. There were 427 tremors with a total duration of 138 hours during April, and 815 tremors in May lasted a total of 72 hours.
Geologic Background. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.
Information Contacts: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan.