Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 17 April
to 16:00 18 April 1997
The current alert level is ORANGE

The level of activity today has been at about the same level as yesterday. Rockfall activity has accounted for the main part of the seismic activity, but there has been a further increase in the number of long-period earthquakes.

The broadband seismic network has detected 31 long-period earthquakes, an increase of 14 on the number detected yesterday. There have been 32 rockfall/pyroclastic flow signals which is a lower intensity than yesterday. These events originated from the active area of the dome above the Galway's Wall. Two hybrid earthquakes were also detected, one of which was located at approximately 2 km depth below the crater.

Views this afternoon from the new observation point on the east ridge of the South Soufriere Hills showed near continuous small rockfall activity from the active southern face of the dome, but none of the debris reached the base of the talus slope. Rockfalls were often associated with ash venting from parts of the active face. There was also some general steaming and ash venting from the area behind the new extrusion, but this was not as intense as has been observed recently.

Total station measurements were taken on the northern triangle today between Windy Hill, St. George's Hill and Farrells. Results from this survey show that, since the last occupation a few days ago, the Windy Hill to St. George's Hill line remains at about the same length whereas the Windy Hill to Farrells line has lengthened by 22 mm and the St. George's Hill to Farrells line has shortened by 19 mm. The long occupation GPS survey between Harris Lookout and Farrells was completed today, and the results are currently being processed.

The alert level remains at ORANGE, because of the unstable dome above the Galway's Wall. Further collapses of the south side of the dome are expected and an escalation of the activity to more serious levels is always possible. Pyroclastic flows could occur without warning in both the Tar River and White River valleys, and these and surrounding areas remain extremely dangerous. Visits to zone C should be kept brief. Zone D should not be occupied tonight.

Montserrat Volcano Observatory