Activity at the Soufriere Hills volcano during this reporting period has continued at a low level. All seismicity was at a low level except during this morning's rain storms.
Only seven rockfalls were recorded during the reporting period. All of these were very small and probably were caused by continued stabilisation of the scar formed during Tuesday's activity. One hybrid event and one regional earthquake (at 16:34 yesterday, 21 September) were recorded by the seismic network. No volcano-tectonic or long-period events were recorded. Broadband tremor and other signals were recorded over most of the seismic network at dawn related to the heavy rain and thunder and lightening activity. A mudflow signal was recorded on the Gages seismometer between 06:25 and 06:35 this morning - some additional mud and rock has been deposited in the lower part of Fort Ghaut.
Visibility was very poor all day and no views of the dome or scar were obtained. A sampling expedition to the Tar River Estate House area was undertaken; these samples and inspection of the deposits should enable the scientists to better understand the events of Tuesday. A temperature of 373 degrees Centigrade (640 degrees Fahrenheit) was obtained at a depth of just 45 cm in the deposits close to the Tar River Estate House.
The GPS survey started yesterday was continued today but not quite completed - data cannot be processed until the survey is finished. The results from the last surveys show shortening of line lengths across the volcano between 25 August and 15 September of about 3 cm, and lengthening of the same lines by about 4 cm between 15 and 18 September. This suggests that Tuesday's events were accompanied by significant deformation which may offer a clue prior to similar events happening again in the future.
MVO scientists are expecting more rockfalls and possibly pyroclastic flows to occur during the next few days as the unstable sides of the new scar feature at English's Crater stabilise. All indications are that the rockfalls and pyroclastic flows will be confined to the Tar River valley area. Dust masks should be worn at all times in ashy environments, which may persist for some time as ash dries out and blows around. Drivers should exercise caution and consideration for other road users, especially when driving through areas still affected by ash or gravel.
The extensive damage which occurred in the Long Ground area on Tuesday night further demonstrates the extreme danger which individuals subject themselves to if they venture into this area or beyond into the Tar River valley. The Tar River and Long Ground areas are now extremely hazardous and we urge individuals who persist in ignoring this advice to think very seriously before making trips to these potentially deadly zones.