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) (Squires, D., ed.). Scientific Event Alert Network Bulletin, 3:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN197806-282080
31.5772°N, 130.6589°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.
Geological Summary. 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 caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim and built an island that was joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4,850 years ago, after which eruptions took place at Minamidake. Frequent eruptions since the 8th century have deposited ash on the city of Kagoshima, located across Kagoshima Bay only 8 km from the summit. The largest recorded eruption took place during 1471-76.
Information Contacts: JMA, Tokyo.