Report on Aira (Japan) — June 1978
Scientific Event Alert Network Bulletin, vol. 3, no. 6 (June 1978)
Managing Editor: David Squires.
Aira (Japan) Earthquake swarms and explosions in mid and late May
Please cite this report as:
Global Volcanism Program, 1978. Report on Aira (Japan). In: Squires, D. (ed.), Scientific Event Alert Network Bulletin, 3:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN197806-282080.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
The air shock from the 22 May explosion broke five windowpanes. Earthquake swarms . . . occurred in mid and late May, correlated with an increase in the number of explosions during the same period. A swarm of exceptionally long duration (16 hours) on 30 May was followed by four explosions on the 31st.
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: JMA, Tokyo.