Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 24 July
to 16:00 25 July 1996

The phase of activity which started on the evening of 20 July continues. There were two periods of intense VT seismicity.

Seismic activity is still dominated by small- to moderate-sized rockfalls from the flanks of the growing lava dome. Approximately 100 rockfall events were recorded during this reporting period, fewer than yesterday when 160 were recorded. The largest rockfalls occurred at 17:22, 18:37 and 19:57 on 24 July and at 10:22 and 15:20 on 25 July. The last of these was of moderate amplitude but lasted for over 5 minutes. It was associated with an ash cloud which drifted to the northwest. One hundred and six (106) VT earthquakes were recorded in this reporting period, a large increase on the 15 recorded yesterday. Most of these occurred in two periods of intense seismicity, between 03:30 and 07:00 and between 13:00 and 15:00 on 25 July. Locations of the VT earthquakes are generally beneath the crater or just slightly to the north at depths of less than 3 km. The small hybrid earthquake activity has increased slightly, with 35 events recorded today. Long-period earthquakes continued at a low level, with 9 being recorded. Intermittent low- to moderate-amplitude broadband tremor was recorded at stations near the crater throughout the reporting period. There were also two periods when a larger amplitude continuous signal was recorded on the Gages seismic station - from 19:27 to 20:00 on 24 July and from 03:17 until 03:37 on 25 July. The nature of the signals suggests that they were associated with flash flooding in Upper Fort Ghaut following heavy rainfall.

Visibility has been poor all day with the dome covered in cloud almost all of the time. The top of the dome was seen from Hermitage very briefly in the afternoon and there appears to be a large spine at the summit of the northern peak.

No gravity, GPS or EDM measurements were made today. Both COSPEC and FTIR measurements of the volcanic gases were made, but the data is still being processed.

Mark Staziuk, Lancaster University, arrived in Montserrat yesterday. He is here as a senior member of the BGS monitoring team. Mark Davies and Elisa Calder leave the island today, after stays of 6 and 8 weeks respectively.

The Soufriere Hills Volcano is still considered to be highly dangerous to people and property on it's eastern and upper western flanks. Visits to the evacuated zone must be kept to a minimum. The Tar River and Long Ground areas to the east and upper Fort Ghaut, Gages Village and Upper Amersham areas to the west are all extremely dangerous. All access roads to these areas remain closed and people should not enter these areas under any circumstances. If they do, they put themselves and others at direct risk of serious injury or death.

Montserrat Volcano Observatory