Activity at the Soufriere Hills volcano during this reporting period has continued at a similar level to that observed during yesterday. Rock falls have continued throughout the day, the largest of which have led to the generation of pyroclastic flows within the Tar River valley.
Seismicity during the day has been dominated by rock fall signals, of which there were 84 today. Other types of seismic signals have been at a lower level than during the last reporting period, with 2 long period events, 3 hybrid events and 4 volcano-tectonic earthquakes recorded by the network. Two periods of semi-continuous rock falls were recorded, between 23:52 on 3 September and 01:06 on 4 September and between 07:48 and 12:00 on 4 September. The latter period included 3 distinct, large signals which were the result of pyroclastic flows in the Tar River valley, the longest of which reached the Estate House. Activity which was ongoing at 16:00 yesterday afternoon (3 September) reached a peak with a pyroclastic flow at 18:35 then died down. All of these flows and rock falls produced ash which drifted north and northwestward overnight, reaching as far as St Johns, but was more towards the west during today. Intermittent broadband tremor was recorded throughout the reporting period. A teleseism (long period wave from a distant earthquake) was recorded by the network at 15:11 today, the source of which as yet remains unknown.
Visibility during the day was moderate, and some observations of the lower flanks of the dome and the rock fall activity were possible. Good observations were possible from the east late yesterday afternoon (3 September), when the scar left by collapses over the previous day was visible and was still the centre of activity. It appeared that a significant volume of material was still in an unstable state and liable to collapse; this has been verified by continued rock falls and pyroclastic flows during today, and more such activity and accompanying ash fall should be expected over the next few days.
EDM measurements were attempted to the Castle Peak reflector, but this has again been covered by ash generated by the pyroclastic flows. Visibility was not sufficiently good to attempt measurements to the Chances Peak reflector, which was cleaned yesterday. The results of the last GPS survey late last week show no large-scale deformation of the volcano.
The COSPEC instrument remains out of commission at present, although attempts are being made at repairs.
Further rockfalls and pyroclastic flows will occur but all indications at the moment are that the pyroclastic flows will be confined to the Tar River Valley area. However, areas affected by associated ashfalls will obviously depend on the direction and strength of the wind at the time. The lack of rain today means that ash is being blown around by the wind, and drivers should exercise additional caution in such conditions. Dust masks should be worn at all times in ashy environments.
The Tar River Valley and surrounding areas continue to be extremely hazardous, and should not be entered under any circumstances. We urge individuals who persist in ignoring this advice to think very seriously before making trips to these highly hazardous zones.
There will be a meeting at Cork Hill Methodist Church tonight, Wednesday 04 September at 19:30, the purpose of which is to discuss with the residents of Cork Hill, Delvins, Weekes and St. George's Hill the impact of the volcano on their community. Everyone is invited.