The long period earthquakes which have dominated the seismic activity during the past few days continued to do so during this current review period. Locations, beneath the crater area and at depths of between 0.5 and 3.0 km, were obtained for several of the larger, magnitude 1.0 to 1.8, earthquakes of this type. Numerous smaller long period earthquakes, which are too small to locate, occurred at a rate of approximately one per minute throughout the review period. The high amplitude broadband tremor observed at the end of the last review period continued until around 04:00 this morning. This tremor then gradually declined to a lower amplitude level and has remained at this level until the end of this review period. Seismic signals associated with rock fall events and small eruptions were recorded, on the seismograph stations nearest to the volcano, throughout the past 24 hours. The largest signals of this type occurred at 20:28 on 27 February and at 06:07 and 08:36 on the morning of 28 February.
EDM measurements were made today, under excellent conditions, on the eastern, western and southern triangles of the volcano. Only the western triangle showed any changes. The line between Amersham and Gages Wall has shortened by 32 millimeters since 14 January; this represents a movement of less than 1 mm per day, and is thus no cause for concern.
Visual observations were made from the helicopter this afternoon in good visibility. Dome growth was seen to be continuing in a number of areas, with the western part of the lava dome still producing the most rock falls, indicative that it is growing most quickly. Steam and gas production continued at a high level.
Sampling at the Brodericks and Amersham springs revealed that drinking water taken from these springs has not been affected by volcanic activity and remains very pure.