Montserrat Volcano Observatory


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


The increased amplitude level of broadband tremor observed at the end of the previous review period continued until about 21:00 last night. This increased broadband tremor then continued, intermittently, until approximately 02:00 this morning before it reverted back to a low to moderate level, which was still evident at 16:00 this evening (21 February). Several volcano-tectonic earthquakes were detected on the seismograph stations nearest to the volcano. The three largest earthquakes of this type, which were recorded on the majority of the seismograph stations, occurred at 14:45 (magnitude 2.0), 15:01 (magnitude 2.2) and 15:41 (magnitude 1.8) on 21 February; they were located at depths of about 3 to 6 km beneath the volcano. Other seismic signals, consistent with that of small rockfalls and eruptions, continued to occur throughout the review period, and were recorded on the seismograph stations nearest to the volcano. The seismic network in Montserrat also recorded a magnitude 6.8 earthquake which occurred off the southern coast of Peru, South America at 08:57 on 21 February.

EDM measurements were completed on the eastern triangle to Castle Peak today. The changes on the lines measured were less than 2 mm from the previous measurement; this continues the trend of very slow movement on the Castle Peak target.

Visual observations were made from the helicopter during the afternoon of 21 February. Moderate to good visibility enabled good views of all of the English's Crater area. Growth continues on the southeastern whaleback and it is now very similar in appearance to the southern whaleback although slightly taller. Several rockfalls were seen from the northwestern part of the new dome towards the base of the Gages Wall and this area appears to be the most active at present. Steam and gas production continues from many areas on and around the new dome.


Montserrat Volcano Observatory