Report on Mikura Seamount (Japan) — December 1982
Bulletin of the Global Volcanism Network, vol. 7, no. 12 (December 1982)
Managing Editor: Lindsay McClelland.
Mikura Seamount (Japan) Earthquake sequence not volcanic
Please cite this report as:
Global Volcanism Program, 1982. Report on Mikura Seamount (Japan) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 7:12. Smithsonian Institution.
33.725°N, 139.408°E; summit elev. -321 m
All times are local (unless otherwise noted)
Beginning 27 December there have been many recorded earthquakes with epicenters in the ocean about 40 km S of Miyake-jima Island (~200 km S of Tokyo; figures 1 and 2). The first felt shock occurred at 1533. At 1537 on 28 December the largest, magnitude [6.4] on the JMA scale, originated at the N edge of the epicentral area. It was followed by gradually decreasing aftershock activity. Earthquake swarms or main shock-aftershock events in the sea around Miyake-jima occurred in July and September 1980, and . . . March 1981. The USGS/NEIS recorded four shocks of magnitude 5 or greater (table 1).
|Figure 2. Hourly and daily (inset) number of earthquakes in the Izu Islands recorded at Miyake-jima Weather Station, 27 December 1982-4 January 1983. Courtesy of JMA.|
Table 1. Earthquakes of Ms >= 5 on 28 December 1982 in the Izu Islands, Japan. Courtesy of the USGS.
Personnel from the Miyake-jima Weather Station visited the summit area (Oyama) on 29 December, but observed no unusual phenomena. The events were interpreted as having been too far from Miyake-jima to be precursors of volcanic activity. A group of shallow earthquakes occurred close to Miyake-jima a few months before the last eruption in 1962.
Information Contacts: JMA, Tokyo; USGS/NEIS, Denver CO, USA