Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 13 September
to 16:00 14 September 1996

Activity at the Soufriere Hills volcano during this reporting period has returned to the level of the few days before yesterday. Dome growth continues, with associated rockfalls at a similar level to yesterday and the return of volcano-tectonic earthquakes is also noted.

The seismicity today has been dominated by rockfall events and volcano-tectonic (VT) earthquakes. One hundred and three (103) VTs were recorded during the 24-hour reporting period, which is much higher than the total recorded yesterday. These occurred in two short swarms between 20:10 and 22:30 yesterday (13 September) and between 06:20 and 08:40 this morning (14 September). These earthquakes were again located at shallow depths (less than 2 km or 1.3 miles) beneath the crater. A total of 123 rockfall events were recorded today, a very similar level to that recorded yesterday. The largest rockfalls occurred at 10:31 and 13:12 today. Thirty seven small hybrid and twelve long period earthquakes were also recorded, both levels similar to the last reporting period. Broadband tremor at a low amplitude was recorded on the Gages seismometer between 22:04 last night and 01:50 this morning.

Visibility was poor again today, with only a few brief clearings late this afternoon allowing glimpses of the dome. Rockfalls appear to be still concentrated on the eastern flank of the dome and some new deposits from small pyroclastic flows were visible near to the Tar River Soufriere. Some of the rockfalls produced small ash clouds which were blown to the west.

EDM measurements were not made today due to bad weather. Repairs were undertaken on the Chance's Peak seismometer today and it is now working again. Brief views of the summit of the dome were obtained by the repair party; no changes were noted since the last viewing a week or so ago.

Further rockfalls and pyroclastic flows will occur as the lava dome continues to grow within English's Crater and its unstable flanks undergo partial collapses. Current indications are that the pyroclastic flows will be confined to the Tar River valley area. Areas affected by associated ashfalls will depend on the direction and strength of the wind at the time. Dust masks should be worn at all times in ashy environments, and drivers should exercise caution and consideration for other road users.

The Tar River Valley and surrounding areas continue to be extremely hazardous, and should not be entered under any circumstances. We urge individuals who persist in ignoring this advice to think very seriously before making trips to these potentially deadly zones.

Several staff changes have taken place at MVO over the past 2 days. Dr William Ambeh left island on Friday, with Richie Robertson taking over as Chief Scientist; Desmond Supersud and Wilkie Balgobin arrived with Mr Robertson from SRU on Thursday. Dr Bill McGuire arrived from the UK today to join the monitoring team; he brings additional expertise in ground deformation to the MVO.

Montserrat Volcano Observatory