Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 22 February
to 16:00 23 February 1997
The current alert level is AMBER

The level of activity at the volcano has remained the same, with a continuation of earthquake swarms. Good visibility late in the afternoon revealed that there were two, new large blocks on the active south-eastern face of the dome.

Seismic activity has been dominated by another swarm of earthquakes with a total of 38 hybrid and 94 volcano-tectonic earthquakes recorded. The swarm extended from 7.00 pm last night to 4:48 am today and was similar to earlier swarms, with volcano-tectonic earthquakes followed by repetitive hybrid earthquakes. This swarm was longer lived, but less intense, than the previous swarms. A period of low-amplitude, continuous tremor followed the swarm. No other swarms have been recorded today which indicates that the 16 hour periodicity has been broken. Otherwise, the level of seismic activity was low, with only 15 rockfalls and no long-period earthquakes recorded. As usual, the earthquakes were too small to be felt.

Visibility was generally poor for the earlier part of the day, but visibility improved in the late afternoon and two large blocks were noted at the top of the active south-eastern face. One of these blocks looks like a tower approximately 30 to 40 m high and appears extremely unstable. There are still several small rockfalls and pyroclastic flows originating on the south-eastern face and on the north of the October dome near the September scar.

No EDM or GPS measurements were made today. As usual, water and ash samples and sulphur dioxide diffusion tubes were collected from sites around Plymouth today.

The dome is currently larger than ever before, and further dome collapses and pyroclastic flows are expected. These will probably follow the recent pattern, but a change in the activity could occur at any time. Visitors to zone C are reminded to remain alert at all times, and spend the minimum possible time in the evacuated zone. Ash levels in Plymouth are hazardous, especially during dry, windy weather, and so it is essential to wear masks in areas affected by ash. Flash floods could cut off access to areas south of Fort Ghaut; visitors should leave that area when it rains. The Tar River Valley and the upper Galway's area are very dangerous and should not be entered at any time.

Brian Baptie of BGS left the island today after a short stay to help with broad band seismology. Commiserations to MVO basketball team who lost a closely fought game against St John's Swipers yesterday evening in the Montserrat Basketball League.

Montserrat Volcano Observatory