The seismic activity during the 24 hour period under review was of a variable nature but long period earthquakes were still the most dominant feature. Many of the larger long period earthquakes (approximate magnitude 1.0 to 1.5) were located beneath the crater area in the depth range 0.5 to 3 km. These earthquakes are currently being recorded at a rate of approximately two per hour. In addition to these long period earthquakes, episodes of high amplitude broadband tremor were observed on the seismograph station at Gages, from approximately 17:00 last night until 04:30 this morning and again from 06:00 until 08:00 this morning, 26 February. This level of broadband tremor has not been seen since 02:00 on the morning of 21 February. Two volcano-tectonic earthquakes were detected during the review period but were too small to obtain an instrumental location. Seismic signals associated with rock fall events and small eruptions have been recorded, on the Gages and Chances Peak seismograph stations, throughout the review period. The largest signal of this type occurred at 15:49 on 26 February and produced a small ash cloud which was visible from the Observatory, the Airport and Long Ground areas.
EDM measurements were made today on the southern triangle between O'Garra's, Galway's Plantation and the Chances Peak target and on the eastern triangle between Long Ground, White's Yard and Castle Peak. An attempt to measure the lines to the Gages Wall reflector was unsuccessful due to haze and possibly ash on the target. None of the measurements made today indicate any change in the rate of deformation of the volcano.
Visual observations were made this morning from the helicopter in very good conditions. The southeastern whaleback has begun to collapse, spalling large blocks into the southeastern moat area. The central and northwestern parts of the dome continue to grow vertically and much of the new dome in these areas is now at a similar height to Castle Peak. Scientists also made observations today from Chances Peak, although conditions were not good. Semi-continuous rock falls were heard from the western and northern parts of the dome. A relatively high level of volcanic gas was also noted in the summit area.