The character of the seismic activity, which has dominated the past two weeks, continued with some variation, throughout the period under review. The rate and amplitude of small hybrid events have reduced during the period accompanied by a slight increase in the level of background broadband tremor. These very small hybrid events are only recorded on the stations closest to the Soufriere Hills volcano and are much too small to be felt or located. The rate of events has varied throughout the period from three to six events per minute. Eight (8) long-period earthquakes were located during the period. These occurred under the crater area at depths ranging from 0.1 to 1.5km. A distinct seismic signal was produced by a large rockfall which occurred at 11:51pm on the 1st February.
EDM measurements were completed today on the Galways-Chances Peak-O'Garra's triangle and on the eastern triangle to Castle Peak. Processing of the data from yesterday's measurements at Castle Peak indicate changes in line length which are less than 5mm. The measurements completed on this triangle today also indicate that no real changes have occurred at this locality. Measurements obtained from the other triangle completed also indicate that there have been no changes in line lengths.
Visual observations were made at midday today from Chances Peak and later during the afternoon from the helicopter. A large rock avalanche from the southern part of the dome was observed by scientists at Chances Peak. The avalanche produced a small convective cloud which deposited very fine-grained ash on the top of Chances Peak. The moat area at English's Crater continues to be filled with rock debris spilled from the actively growing parts of the new dome. Activity continues to be concentrated in two main areas, the northern and southern sections of the dome with vigorous steaming from the top central sections. Continued vertical growth of the entire dome has allowed it to become more visible from several areas on the western flanks of the volcano. Should dome growth continue at its current rate, it is expected that the dome would become visible to more areas to the west. This increased visibility of the actively growing lava dome should be no cause for increased concern by residents.
Dr Simon Young of the BGS returned to the U.K. today after spending the last 2 1/2 months on island assisting with monitoring activities at the Soufriere Hills volcano.