Report on Kujusan (Japan) — May 1996
Bulletin of the Global Volcanism Network, vol. 21, no. 5 (May 1996)
Managing Editor: Richard Wunderman.
Kujusan (Japan) Seismic activity increases, but there is no ashfall
Please cite this report as:
Global Volcanism Program, 1996. Report on Kujusan (Japan) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 21:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199605-282120.
33.086°N, 131.249°E; summit elev. 1791 m
All times are local (unless otherwise noted)
The increased seismicity that began in late March and early April (BGVN 21:02 and 21:03) continued during May. The total number of earthquakes in May was 423, of which 283 occurred on the 14th. No volcanic tremor was observed. The plume height remained at 100-400 m for most of the month, but rose to 600 m on 14 May. There were no ashfalls.
Geologic Background. Kujusan is a complex of stratovolcanoes and lava domes lying NE of Aso caldera in north-central Kyushu. The group consists of 16 andesitic lava domes, five andesitic stratovolcanoes, and one basaltic cone. Activity dates back about 150,000 years. Six major andesitic-to-dacitic tephra deposits, many associated with the growth of lava domes, have been recorded during the Holocene. Eruptive activity has migrated systematically eastward during the past 5000 years. The latest magmatic activity occurred about 1600 years ago, when Kurodake lava dome at the E end of the complex was formed. The first reports of historical eruptions were in the 17th and 18th centuries, when phreatic or hydrothermal activity occurred. There are also many hot springs and hydrothermal fields. A fumarole on Hosho lava dome was the site of a sulfur mine for at least 500 years. Two geothermal power plants are in operation at Kuju.
Information Contacts: Japan Meteorological Agency (JMA), Volcanological Division, Seismological and Volcanological Department, 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan.