Report on Izu-Oshima (Japan) — May 1993
Bulletin of the Global Volcanism Network, vol. 18, no. 5 (May 1993)
Managing Editor: Edward Venzke.
Izu-Oshima (Japan) Earthquake swarm and volcanic tremor
Please cite this report as:
Global Volcanism Program, 1993. Report on Izu-Oshima (Japan). In: Venzke, E. (ed.), Bulletin of the Global Volcanism Network, 18:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199305-284010.
34.724°N, 139.394°E; summit elev. 758 m
All times are local (unless otherwise noted)
Continuous volcanic tremor began on the evening of 30 May at the active Mihara-yama cone, reaching peak amplitude at about 2300 that day. The next night, an increase in shallow earthquake activity began in the summit area. Both the earthquake swarm and tremor had stopped by 5 June. This was the first episode of volcanic tremor recorded since April 1990. Weak and steady steaming from the Mihara-yama crater continued without change throughout the period of increased seismicity.
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.