Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 04 June
to 16:00 05 June 1996

Volcanic activity at the Soufriere Hills Volcano has been at a moderate level today, dominated by small to moderate-sized rockfalls. There was a small mudflow near the Gages seismic station shortly after midnight.

Seismicity at the volcano continues to be dominated by the occurrence of rock fall signals. There were 61 of these, an increase compared to 27 yesterday. The largest rockfalls were recorded at 19:23 on 4 June and 05:32, 09:39 and 14:53 on 5 June. No ashfall was reported from any of these events. There were 11 hybrid events today and 13 long period earthquakes. There have been brief periods of intermittent low-amplitude broadband tremor throughout the reporting period.

Sustained broad-band tremor was recorded on the Gages seismic station from 00:05 to 00:39 this morning, and with very high amplitude from 00:15 to 00:23. It was not recorded on any other seismic station and must have been produced by something very localised, most likely a small mudflow near the station. The nature of the seismic signal, building gradually to a peak and then slowly decreasing, is similar to previous mudflow signals. Muddy water was seen in Fort Ghaut in Plymouth at the time and a later inspection showed a thin deposit of fresh material in Fort Ghaut, at most 1 mm thick.

Cloud cover prevented clear views of the summit of the volcano throughout the day.

No EDM measurements were made due to the poor weather conditions. Analysis of the dry tilt measurements conducted at the Brodericks tilt station yesterday show some changes in line lenghts since this station was last occupied on 5 January, 1996. However, the cumulative error on these measurements was quite large and may account for the changes observed. This station would be reoccupied during the next few days in an attempt to reduce the errors and obtain more conclusive data.

COSPEC measurements of the SO2 gas concentration in the volcanic plume were made along the coastal road in Plymouth today. The results of these measurements are presently being processed. The results obtained yesterday show an average SO2 flux of about 240 tonnes per day. This is slightly higher than most of the recent results, but is still a very low value.

Scientists at the Montserrat Volcano Observatory view the situation at the Soufriere Hills Volcano with grave concern. Visits to the evacuated zone should be kept to a minimum. The Tar River, Long Ground and Whites areas are extremely dangerous due to the frequent occurrence of pyroclastic flows in the Tar River valley. People should not enter these areas under any circumstances. If they do, they put themselves at direct risk of serious injury or death.

Montserrat Volcano Observatory