Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 10 March
to 16:00 11 March 1997
The current alert level is AMBER

The increased level of seismicity seen yesterday continued today in the form of another earthquake swarm. The swarm lasted from 02:55 until 14:16 and produced 25 VT earthquakes and 79 hybrid earthquakes. Throughout the reporting period there have been 10 rockfall signals recorded by the MVO network. Some of the larger VT events developed into rockfalls with accompanying ash clouds. This is in contrast to yesterdays swarm when there were no rockfalls during the swarm. The continued occurrence of rockfalls indicates that the dome is still growing. Low level tremor has also been recorded at Gages seismic station several times during the day. A teleseismic signal from a distant earthquake was also recorded just around 16:00 this afternoon

Views of the crater area have been severely hampered by the poor weather conditions which have prevailed for most of the day. Numerous ash clouds have been observed during the afternoon which have originated from rockfalls on the eastern and southern sides of the dome. The largest rockfall seen to date over the Galway's Wall was observed via the CCTV. Bramble tower also reported the production of pyroclastic flows from the northern part of the dome.

The long occupation GPS experiment between Harris Lookout and Hermitage was completed this morning. The results of this survey show that the Hermitage site has moved some 20 millimetres toward the north-east since the line was last measured on January 18th. The GPS equipment is currently being re-deployed to check this result.

No EDM measurements were made today due to the unfavourable atmospheric conditions.

Dr Tim Druitt (Universite Blaise Pascal, France) and Mr Wilkie Balgob in (SRU) both left the island this morning after completing tours of duty at MVO. Dr Paul Cole (University of Luton, UK) has arrived to assist in volcanological and ground deformation aspects of the monitoring.

During the last few days the eastern slope of the dome has become increasingly unstable. Given that the dome is now large and continuing to grow, a large collapse and pyroclastic flows could happen with little warning. It is dangerous to spend the night in evacuated areas, because the situation could worsen rapidly over a period of a few hours. People entering Zone C are reminded to remain alert at all times, and spend the minimum possible time in the evacuated zone. The Tar River Valley and the upper Galway's area are very dangerous and should not be entered at any time.

Montserrat Volcano Observatory