Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 09 September
to 16:00 10 September 1996

Activity at the Soufriere Hills volcano during this reporting period has continued at about the same level as observed during the previous 24 hours; poor visibility has again prevented any sightings of the dome.

The seismicity has again been dominated by the occurrence of volcano-tectonic (VT) earthquakes. One hundred and fifty nine (159) volcano-tectonic earthquakes were recorded during the 24-hour reporting period. Most of these occurred in a single swarm between 02:00 and 06:50 this morning (10 September), the remainder occurring between 16:00 and 17:50 yesterday afternoon (9 September). All of the VTs for which locations were calculated again occurred at shallow depths beneath the volcano. A total of 35 rockfall events were recorded today, the largest occurring at 19:32 last night and at 02:00 this morning. A number of the rockfalls produced small ash clouds which drifted westwards from the volcano. Twelve small hybrid and four long period earthquakes were also recorded. Broadband tremor at a very low amplitude was recorded on the Gages seismometer throughout the reporting period; enhanced steam production from the volcano along with water running in Fort Ghaut were likely causes of this tremor.

Visibility was generally poor throughout the day because of low cloud cover and rain. Brief clearances were sufficient to see ash and gas emissions from the dome but no details of any new developments on the dome were seen.

EDM measurements were not made today because of the continued low cloud cover. The COSPEC instrument was sent to the manufacturers today for repairs; it is expected to be back in action in a week or so.

Calculations of the volume of the dome suggest that the growth rate reached the highest level yet during the current eruption from mid- to late July through to late-August, but it appears to have declined somewhat since then - the scientists are awaiting better visibility to confirm this.

Further rockfalls and pyroclastic flows will occur as the lava dome continues to grow within English's Crater, but indications at the moment are that the pyroclastic flows will be confined to the Tar River valley area. Areas affected by associated ashfalls will obviously depend on the direction and strength of the wind at the time. The rainfall will make some ash-coated roads very slippery so extreme care should still be taken when driving in ash affected areas. 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 highly hazardous zones.

Montserrat Volcano Observatory