Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 23 July
to 16:00 24 July 1996

The phase of activity which started on the evening of 20 July continues but the level has declined slightly during this reporting period.

Seismic activity is still dominated by small- to moderate-sized rockfalls from the flanks of the growing lava dome. Approximately 160 rockfall events were recorded by the seismic system during this reporting period, which is about the same level as yesterday. The largest rockfalls occurred at 04:39, 12:06 and 12:21 on 24 July. Fifteen (15) VT earthquakes were recorded in this reporting period, the same number as yesterday. 10 of these occurred between 01:00 and 07:30 on 24 July. Locations of the VT earthquakes are generally beneath the crater or just slightly to the north and at depths of 3 to 4.5 km. The small hybrid earthquake activity has decreased noticeably, with only 9 events recorded today. Long-period earthquakes were also scarce, with only one being recorded. Intermittent low- to moderate-amplitude broadband tremor was recorded at stations near the crater throughout the reporting period.

Visibility has been poor all day with the dome covered in cloud most of the time. During the early morning, there were some brief views of the lower flanks of the dome from the east when a few rockfalls were noted. All of these were on the northeast and northern flanks. The only ash cloud seen was one generated by a rockfall at 13:03 on 24 July. Many of the other rockfalls will have generated small ash clouds.

Gravity and GPS measurements were made today at stations along a radial line on the western flank of the volcano, ending at Chances Peak. Further COSPEC measurements of the SO2 flux were carried out, but the data is still being processed.

EDM measurements were made yesterday on lines in the eastern triangle. The lines from Long Ground and Whites to Castle Peak show shortening of about 8 cm over the four days since they were last measured.

Peter Francis, Open University, and Clive Oppenheimer, University of Cambridge, arrived in Montserrat on 20 July. John Stix, Montreal University, arrived on 21 July. They will be carrying out gas measurements; commissioning a new COSPEC to replace the current machine which is on loan, and resuming Fourier Transform Infra Red Spectroscopy measurements. Mick Murphy, Bristol University, left Montserrat today after a short visit to study some of the pyroclastic deposits.

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