Montserrat Volcano Observatory


Daily Report
Report for the period 16:00 on 12 Jan. 1996
to 16:00 on 13 Jan. 1996


The seismicity during this period has been dominated by the occurrence of the near-repetitive hybrid earthquakes which started at approximately 15:50 on January 12. These events are generally similar to those observed about one week ago and in September and November 1995. The rate of occurrence of these events has varied from about 1 per two minutes for the period 16:00 to 20:00 on January 12, 1 per minute for the period 20:00 on January 12 to 07:30 on January 13 and 1 per several minutes for the period 07:30 to 16:00 on January 13. A total of more than 1000 earthquakes have been recorded during this period, of which 114 have been located for the time interval 16:00 to 23:00 on January 12. Similar to last weekend's sequence, these events are clustered beneath the crater area at depths in the range 0 to 3 km. Processing of the remainder of the events continues. Two events recorded at the Gages and Long Ground seismic stations at 18:38 on January 12 and 01:19 this morning were probably due to small shallow explosions or rockfalls within English's Crater. The event at 18:38 was associated with reports of very light ashfall in Plymouth.

EDM measurements were made today on the White's Yard to Castle Peak line and on the St. George's Hill - Windy Hill - Farrells triangle. No significant change within the errors of the technique was noted from previous occupations for both of these measurements.

No visual observations of the crater could be made from the helicopter or the crater rim because of the very low cloud cover on the volcano.


Montserrat Volcano Observatory