Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 on 12 Feb. 1996
to 16:00 on 13 Feb. 1996

Seismicity at the beginning of the period under review was very low with tiny hybrid earthquakes occurring about every 10 minutes. About 03:00 on 13 February these hybrid earthquakes began to occur more frequently reaching about 1 per minute. There was also a slight increase in amplitude of these earthquakes with the majority having magnitudes between 0.3 and 0.5. However, these earthquakes are still so small they are only being observed on the nearest seismic stations to the volcano and thus their locations can be determined. At 08:00 on 13 February an episode of continuous low to moderate broad band tremor commenced and was still occurring at the end of the period under review. Close inspection of the seismic record from the station at Gages showed the continued presence of the small hybrid events imbedded in the broad-band tremor. Other seismic signatures observed throughout the day were probably the result of small rockfalls

EDM measurements were made on the Galways-Chances Peak-O'Garra's triangle today. The O'Garra's-Chances Peak line decreased by 1.4cm since its last occupation on the 1 February. There were no changes on the other segments of this triangle since its last occupation.

Visual observations of the volcano were made from the helicopter late this morning and from Chances Peak during the late afternoon. Clear views were obtained of the south-eastern part of the dome which appears to be one of the main foci of growth at present. Several small rockfalls were observed from this surface. Copious amounts of steam continue to be emitted from the top central part of the dome. Two new protrusions were observed in the west central part of the dome; these new features have grown during the past two days. Brief views from the top of Chances Peak late this afternoon indicate that dome growth continues on the western part; rockfalls were observed from this area. The visit to Chances Peak indicates that the levels of acidic aerosols (mainly SO2, HS and HCl) continue to be relatively high at the top of Chances Peak. A strong south-easterly wind continue to channel some of these aerosols into the Gages valley.

Results from analysis of rain water samples collected in the Gages valley on 9 February were received from the Volcano Observatory in Guadeloupe today. The results indicate that concentration of sulphates, fluorides and chlorides are still well below levels which could have a deleterious effect on human health.

Mr David Galloway of the British Geological Survey jointed the monitoring team today. Mr Galloway would assist in monitoring of seismological aspects of the Soufriere Hills volcano.

Montserrat Volcano Observatory