Report on Asamayama (Japan) — April 1991
Bulletin of the Global Volcanism Network, vol. 16, no. 4 (April 1991)
Managing Editor: Lindsay McClelland.
Asamayama (Japan) Continued steam emission; seismicity increases after 2 months of quiet
Please cite this report as:
Global Volcanism Program, 1991. Report on Asamayama (Japan). In: McClelland, L. (ed.), Bulletin of the Global Volcanism Network, 16:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199104-283110.
36.406°N, 138.523°E; summit elev. 2568 m
All times are local (unless otherwise noted)
Strong seismicity . . . declined during February and March 1991. Only 19 earthquakes and no tremor episodes were recorded in March. Seismicity increased again 8-18 April and a monthly total of 250 earthquakes and 17 tremor episodes were recorded (figure 13). Steam emission remained unchanged with a plume height of a few hundred meters.
|Figure 13. Daily number of recorded earthquakes (top) and tremor episodes (bottom) at Asama, January 1989-early May 1991. Arrow marks small ash eruptions on 20 July 1990. Courtesy of JMA.|
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: JMA.