Montserrat Volcano Observatory


Morning Update
Report for the period 16:00 01 August
to 07:00 02 August 1996


The activity at the Soufriere Hills volcano during this reporting period continued at a slightly higher level compared to that observed during the previous 24 hours. Five periods of sustained, low- to moderate-amplitude, low-frequency, harmonic tremor were recorded at intervals of about 3 hours. These episodes started with small, near-repetitive, hybrid earthquakes which increased in frequency and sometimes amplitude until they formed a continuous tremor. After a period of sustained peak amplitude, the signal then decayed first into smaller hybrid events and then background. These episodes of repetitive hybrid earthquakes and harmonic tremor, which usually lasted about 90 minutes, are probably associated with magma migration from shallow depths to the surface or near-surface as the process of dome growth at the Soufriere Hills continues. Several small- to moderate-sized rockfalls also occurred, with the largest being recorded at 19:24 and 20:29 on 01 August and 01:08, 01:24 and 01:45 on 02 August. Several small long-period events and a few volcano-tectonic earthquakes were recorded.

Visibility was very poor during the early morning period.

While the current phase of activity at the Soufriere Hills volcano continues, hazards in some areas of the evacuated zone have increased significantly. In particular, we expect significant-sized pyroclastic flows to occur more frequently in the Tar River Valley area. These will obviously be associated with ash clouds which will be blown on the wind, with areas affected by ashfall being determined by the wind direction and strength at that time. The Tar River Valley and surrounding areas are now extremely hazardous, and should not be entered under any circumstances. If activity continues, there is a risk that flows or ash surges may come over Farrells' Wall and the upper reaches of some of the ghauts closest to the Tar River Valley. People are, therefore, advised not to work these areas. We also urge individuals who continue to ignore this advice to think very seriously before making trips to these highly hazardous zones.


Montserrat Volcano Observatory