The monthly total of earthquakes was 254 for September, 270 for October, and 313 for November. The plume height usually remained at 200-400 m during September, but reached 700 m four times. During October and November the plume height was mostly at 100-300 m, but on 11 and 29 October it reached 600 m, and on 24 November it was 700 m high. On 28, 29, and 30 November, 15 small-amplitude volcanic tremors were observed. Prior to that, tremor was last detected on 29 March 1996.

Geological Summary. 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: Volcanological Division, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan.