Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 01 November
to 16:00 02 November 1996
The current alert level is ORANGE.

The level of activity at the volcano has increased again during the 24-hour period, with the continuation of an intense swarm of volcano-tectonic earthquakes. The swarm is the largest recorded since the start of dome growth last November, and indicates a significant increase in magmatic activity at the volcano.

The swarm began at 00:27 on 1 November, and so far 393 earthquakes have been recorded, with 327 of these occurring during the last 24 hours. During the most intense period, earthquakes were occurring at a rate greater than one every two minutes. The magnitude of the earthquakes has been relatively large, and many of the events were larger than those recorded in recent swarms. However, none of the earthquakes have been reported felt.

There have been two groups of earthquakes, both located beneath the crater. Most of them were shallow, at depths of above 2 km, and were similar to events in recent swarms. However, between 21:00 last night and 07:30 this morning a number of significantly deeper earthquakes were recorded, with depths of 3 to 4 km. There have been very few other seismic signals. One rockfall signal at 11:53 was associated with a small ash cloud.

The viewing conditions were variable for most of the day. Two helicopter observation flights were made, and no major changes in the dome were seen, apart from an area of increased steam and sulphur dioxide production from northwest of the new dome, and there is possibly a new intrusion taking place there. Also, a small new spine was seen near this location. There has been no new material deposited in the upper Tar River valley.

An EDM survey was carried out on the eastern triangle between Long Ground, Whites and Castle Peak. The line lengths to Castle peak have shortened by about 9 cm since they were last measured on 23 October. This rate of shortening, of about 1 cm per day, is similar to the rate that has occurred since mid-July.

A GPS survey was made of a set of four points on the flank of the volcano. The preliminary processing of these data show an increase of about 2 cm in line lengths from west to east across the volcano. The significance of these measurements is not yet known, and the survey will be repeated as soon as conditions permit.

COSPEC measurements were made both this morning and afternoon to determine the amount of sulphur dioxide coming from the volcano. The average flux is 300 tonnes per day, which is a decrease since the last measurements two days ago.

The MVO scientists are extremely concerned about the change in activity during the past 24 hours, and recommended an increase in the alert level from Amber to Orange at 06:15 this morning. The earthquake swarm and other changes noted today may be precursors to another explosive eruption. We stress that the volcano is in a very dangerous state, which could increase in level over a short period. All residents are urged to follow the recommendations laid out in the alert procedures, and listen to Radio Montserrat.

Montserrat Volcano Observatory