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Report on Izu-Oshima (Japan) — March 1988

Scientific Event Alert Network Bulletin, vol. 13, no. 3 (March 1988)
Managing Editor: Lindsay McClelland.

Izu-Oshima (Japan) Tremor and discrete seismic events; steam emission

Please cite this report as:

Global Volcanism Program, 1988. Report on Izu-Oshima (Japan). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 13:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198803-284010.

Volcano Profile |  Complete Bulletin


Izu-Oshima

Japan

34.724°N, 139.394°E; summit elev. 758 m

All times are local (unless otherwise noted)


Continuous tremor resumed on 18 January, then became intermittent on 15 February, although its amplitude increased 27 February-6 March (figure 14). As of 5 April, tremor was continuous but of low amplitude. Earthquake activity increased sharply 3-4 March (figure 15), with most events apparently centered under the summit cone. The number of events counted by the instrument in the caldera exceeded 275 on 3 March and 502 on the 4th, but declined to a typical rate of 13/day on 6 March. A white steam plume continuously rose 300-800 m above the summit crater. On 18 March, an 1,800-m white plume was observed from the Oshima Weather Station, the highest plume seen since the 18 November 1987 eruption.

Figure (see Caption) Figure 14. Amplitude of volcanic tremor at Oshima, 1 May 1987-31 March 1988. Courtesy of JMA.
Figure (see Caption) Figure 15. Number of earthquakes/day at Oshima, 17 March 1987-31 March 1988. Courtesy of JMA.

Geologic Background. Izu-Oshima volcano in Sagami Bay, east of the Izu Peninsula, is the northernmost of the Izu Islands. The broad, low stratovolcano forms an 11 x 13 km island and was constructed over the remnants of three dissected stratovolcanoes. It is capped by a 4-km-wide caldera with a central cone, Miharayama, that has been the site of numerous historical eruptions. More than 40 cones are located within the caldera and along two parallel rift zones trending NNW-SSE. Although it is a dominantly basaltic volcano, strong explosive activity has occurred at intervals of 100-150 years throughout the past few thousand years. Historical activity dates back to the 7th century CE. A major eruption in 1986 produced spectacular lava fountains up to 1600 m height and a 16-km-high eruption column; more than 12,000 people were evacuated from the island.

Information Contacts: JMA.