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Report on Mikura Seamount (Japan) — October 1990

Mikura Seamount

Bulletin of the Global Volcanism Network, vol. 15, no. 10 (October 1990)
Managing Editor: Lindsay McClelland.

Mikura Seamount (Japan) Three bursts of seismicity near Mikura Seamount

Please cite this report as:

Global Volcanism Program, 1990. Report on Mikura Seamount (Japan) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 15:10. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199010-284043

Mikura Seamount


33.725°N, 139.408°E; summit elev. -321 m

All times are local (unless otherwise noted)

A swarm of earthquakes began at 0624 on 5 October 1990, in the sea ~20 km SW of Mikura-jima Island (figure 3). A second burst occurred 13 October, following a gradual decline from the 5th, and a third burst occurred on 21 October (figure 4). A total of about 30 shocks were felt by residents on Mikura-jima and nine were felt on Miyake-jima Island (at Miyake-jima Weather Station), ~40 km NNE of the epicentral area. The largest event was M 4.3 and occurred on 27 October. Depths of most of the located events ranged from 20 to 30 km, although depth control was poor.

Figure (see Caption) Figure 3. Epicentral distribution of earthquakes (M >= 3.0) off Mikura-jima, October 1990. Courtesy of JMA.
Figure (see Caption) Figure 4. Daily number of located earthquakes off Mikura-jima, October 1990. Courtesy of JMA.

The swarm occurred in the vicinity of Mikura Seamount, a cone-shaped feature with a summit ~300 m below sea level and 1,400 m above the surrounding sea floor. No surface phenomena were reported in the area in October, nor have any been reported in historical time. The last swarm near this site took place in December 1982, and was more vigorous, including one M 6.4 event.

Geological Summary.

Information Contacts: JMA.