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Report on Akan (Japan) — March 1982

Scientific Event Alert Network Bulletin, vol. 7, no. 3 (March 1982)
Managing Editor: Lindsay McClelland.

Akan (Japan) Sudden increase in local seismicity

Please cite this report as:

Global Volcanism Program, 1982. Report on Akan (Japan) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 7:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198203-285070.



43.384°N, 144.013°E; summit elev. 1499 m

All times are local (unless otherwise noted)

On 21 March a strong (M 6.9) earthquake occurred near Urakawa, off the S coast of Hokkaido and 182 km SW of Akan. Local seismicity at Me-Akan increased after the earthquake, but the JMA has reported that there is no evidence of a causative relationship. The total number of seismic events recorded in March was 411 (table 1). The numbers of recorded seismic events at Me-Akan for 1977-81 are 97, 45, 491, 254, and 194.

Table 1. Number of seismic events recorded at Me-Akan during 19-31 March 1982. Courtesy of JMA.

Date Number of Events
19 Mar 1982 1
20 Mar 1982 3
21 Mar 1982 9
22 Mar 1982 55
23 Mar 1982 63
24 Mar 1982 26
25 Mar 1982 84
26 Mar 1982 24
27 Mar 1982 30
28 Mar 1982 13
29 Mar 1982 31
30 Mar 1982 50
31 Mar 1982 22

Geologic Background. Akan is a 13 x 24 km caldera located immediately SW of Kussharo caldera. The elongated, irregular outline of the caldera rim reflects its incremental formation during major explosive eruptions from the early to mid-Pleistocene. Growth of four post-caldera stratovolcanoes, three at the SW end of the caldera and the other at the NE side, has restricted the size of the caldera lake. Conical Oakandake was frequently active during the Holocene. The 1-km-wide Nakamachineshiri crater of Meakandake was formed during a major pumice-and-scoria eruption about 13,500 years ago. Within the Akan volcanic complex, only the Meakandake group, east of Lake Akan, has been historically active, producing mild phreatic eruptions since the beginning of the 19th century. Meakandake is composed of nine overlapping cones. The main cone of Meakandake proper has a triple crater at its summit. Historical eruptions at Meakandake have consisted of minor phreatic explosions, but four major magmatic eruptions including pyroclastic flows have occurred during the Holocene.

Information Contacts: JMA, Tokyo.