Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 on 20 March 1996
to 16:00 on 21 March 1996

The level of seismic activity has been low over the last 24 hours. A variety of signals have been recorded, from long-period, hybrid and volcano-tectonic earthquakes. Only 15 long-period signals were recorded, compared with up to 40 per day over the previous few days. Two small volcano-tectonic earthquakes were located, one at a depth of 2 km beneath Bethel and the other at 3 km beneath Windy Hill.

The eastern, northern and western EDM triangles were all measured today. The results show only minor changes in line lengths since the triangles were last measured, consistent with continued slow deformation of the volcano. The large change in the Windy Hill to Farrell's line length recorded yesterday appears to be due to an error. The line was remeasured today, and shows only 3 mm of shortening over the last 9 days. The lines to the Gages Wall reflector were measured for the first time since March 3rd, after the reflector was cleaned this afternoon. The lines have shorted by about 15 mm over the last 18 days, thus there is no evidence that the Gages Wall is unstable at present.

Visual observations were made today during several helicopter flights and from the crater rim at Chances Peak. High amounts of steam and gas emission from the crater have continued, particularly from the central and southern parts of the dome. Recent dome growth was observed in the south of the dome, and that section is now nearly as high as the current highest point on the dome, which is near the Gages Wall. The highest point is still at about the same height, at 2860 ft, as it was last week. Only a few rockfalls have occurred today, and as a result the amount of ash emitted has been low.

Dr Peter Baxter returned to the UK today.

Montserrat Volcano Observatory