Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 on 16 Feb. 1996
to 16:00 on 17 Feb. 1996

The main feature of the seismic activity during the period under review was a magnitude 3.3 earthquake which occurred at 07:15 on 17 February. The earthquake had an instrumental location 4.5 km east of the island, a depth of approximately 13 km and was reported felt at Bramble airport tower. Episodes of low to moderate broad band tremor were observed on two occasions during the review period; the first at about 00:00 and the second at about 04:00, lasting for about 2 and 4 hours, respectively. A small hybrid earthquake (dominant frequency of 3-5 Hertz) was recorded, on the seismic stations nearest to the volcano, at 22:47 on 16 February. Other smaller hybrid earthquakes are still being recorded on the seismic stations at Gages and Chances Peak. Other seismic signals, often associated with small rockfalls, continue to occur at regular intervals. Larger signals of this type were recorded at 03:19 and 05:25 on 17 February.

An attempt was made to occupy the EDM triangle between Dagenham, Amersham and the Gages Wall reflector; the steam and aerosol haze within the Gages valley prevented adequate sighting of the target and no measurements were possible. An attempt to occupy the eastern EDM triangle late in the afternoon of 17 February was also unsuccessful due to low cloud.

Good views of English's Crater were obtained from the helicopter during the morning of 17 February. Growth has continued on the new whale-back feature running southeastwards from the central part of the new dome; it is not yet as long or high as the southern whale-back, but appears to have grown to its current size more quickly. A second area of mainly vertical growth was noted in the western part of the new dome; this area was not well seen due to the high steam production in the crater, but there appear to be several spines within the area.

Mr Uche Osuji joined the MVO monitoring team for the first time this morning; he is a member of the Seismic Research Unit (UWI) and will be helping with the instrumental and computing side of the monitoring exercise.

Montserrat Volcano Observatory