ERUPTION OF MIYAKEJIMA VOLCANO, JAPAN


(18 October 2000: by Japan Meteorological Agency and Japan Coast Guard)

Miyakejima volcano, Japan started eruption on 27 June 2000. The last eruption of Miyakejima volcano was in 1983.
Since 26 June 2000, vigorous earthquake swarm began. Japan Meteorological Agency (JMA) issued 'Volcanic Alert' just after the start of the earthquake swarm.
Submarine eruption was observed on 27 June. The hypocenters of the earthquakes migrated westward and vigorous seismic swarm started near Niijima-Kodujima islands.
Erathquake swarm just beneath the summit of Miyakejima started on 4 July. The first summit eruption occurred on 8 July. The eruption was small but a large collapse crater was observed after the eruption. Summit collapse continued also after the event. Summit eruptions with volcanic ash were observed on 14-15 July, 10 August. After the eruption on 10 August, frequent summit eruptions were observed and the most large eruption occurred on 18 August. The eruption on 29 August was accompanied with low temparature surge, which reached the sea. All of the people in the island evacuated after the eruption.
In present, the seismic activity of Miyakejima has declined but very large flux of SO2 is measured; 1,000-3,000ton/day.
The daily flux of SO2 is shown here. (Revised on 25 July 2006)

As the volcanic activity has declined, the islanders came home since 1 February 2005.


Major eruptions of Miyakejima volcano in this activity

Date/Time
8/10 06:30-13:00
8/18 17:02-18:30
8/29 04:35-05:30
Smoke height
(m)
8000
14000
8000
Tremor
(10-5m/s)
25
73
65
Infrasonic data (Pa)
16
>20
14
Remarks
Ash fall from NE to east. Volcanic blocks to the flank.Ash fall almost all of the island. Blocks fell also in the town.Ash fall from NW-N-SE.
Low temperature pyroclastic flow reached to northern seacoast.


More information on the eruption of Miyakejima is shown in WWW of
Earthquake Research Institute, Tokyo University
Geological Survey of Japan

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