Report on Asamayama (Japan) — November 1996
Bulletin of the Global Volcanism Network, vol. 21, no. 11 (November 1996)
Managing Editor: Richard Wunderman.
Asamayama (Japan) Seismic activity continues
Please cite this report as:
Global Volcanism Program, 1996. Report on Asamayama (Japan) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 21:11. Smithsonian Institution.
36.406°N, 138.523°E; summit elev. 2568 m
All times are local (unless otherwise noted)
Seismicity was high during September: The monthly total number of earthquakes at Station B, 2 km S from the summit, was 874. The daily total number of earthquakes was 30-50 with a maximum of 71 on 3 September. Seismicity decreased in October: the total number of earthquakes recorded at station B was 702.
An abrupt increase in seismicity took place on 10 November when 216 earthquakes were recorded. Activity decreased the next day and then increased on 27 November. The monthly total number of earthquakes was 769.
Geologic Background. Asamayama, Honshu's most active volcano, overlooks the resort town of Karuizawa, 140 km NW of Tokyo. The volcano is located at the junction of the Izu-Marianas and NE Japan volcanic arcs. The modern Maekake cone forms the summit and is situated east of the horseshoe-shaped remnant of an older andesitic volcano, Kurofuyama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic shield volcano was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 BP, and by growth of the Ko-Asama-yama lava dome on the east flank. Maekake, capped by the Kamayama pyroclastic cone that forms the present summit, is probably only a few thousand years old and has an historical record dating back at least to the 11th century CE. Maekake has had several major plinian eruptions, the last two of which occurred in 1108 (Asamayama's largest Holocene eruption) and 1783 CE.
Information Contacts: Volcanological Division, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan.