Residents of communities near to St. Vincent’s La Soufriere volcano were, on Wednesday, encouraged to heighten their preparedness in the event that it becomes necessary to evacuate at short notice.
The warning from the National Emergency Management Organisation (NEMO) came as scientists have noted a change in seismic activity associated with the ongoing effusive eruption of the volcano.
And while NEMO is encouraging residents in the Red and Orange Volcanic Hazard Zone to increase their preparedness, it said that the alert level remains at “Orange” and no evacuation order or notice has been given.
NEMO said that earthquakes associated with the ongoing eruption of La Soufriere continue to occur from time to time and some of the largest ones may be felt.
The volcano continues to be closely monitored by a locally based team consisting of scientists from the Soufriere Monitoring Unit, The UWI Seismic Research Centre (SRC) and the Montserrat Volcano Observatory (MVO).
This team, which is led by Vincentian geologist, Professor Richard Robertson, works closely with an extended group based at the SRC in Trinidad, and use a variety of techniques that are constantly being improved and upgraded to monitor the volcano.
Orange is the third highest on the four-level scale, with red being the highest.
The orange alert means there is a highly elevated level of seismicity or fumarolic activity or both and that eruptions may occur with less than 24 hours’ notice.
With the orange alert, residents of the northern third of St. Vincent are to prepare to evacuate at short notice, should such an order be given.
On Wednesday, NEMO said that monitoring scientists at the Belmont Observatory, near Rose Hall, have noted a change in seismic activity associated with the ongoing eruption of the volcano.
The team is led by scientists from the UWI Seismic Research Centre (SRC).
“Up until [Tuesday] 23 March 2021, the seismic activity had been dominated by very small low-frequency events which were associated with the ongoing extrusion of the lava dome,” NEMO said in a press statement.
“These were almost always only recorded at the seismic station closest to the dome. Starting at approximately 10:30 local time (14:30 UTC) on 23 March 2021, the monitoring network recorded a swarm of small low-frequency seismic events which lasted for about 45 minutes.
“These events were different from previous activity in that they were also recorded on other stations.”
NEMO said that the seismic events “were probably associated with magma movement beneath the dome, although their depth cannot be determined”.
It was the first time that scientists had seen such a swarm since the seismic network was upgraded in early 2021.
“Starting at 16:53 local time (20:53 UTC) on 23 March 2021, the monitoring network started recording volcano-tectonic (VT) earthquakes,” NEMO said.
“These earthquakes are normally associated with underground fractures of the rock mass and are commonly generated by magma pushing through an unyielding rock mass.
“The volcano-tectonic earthquakes were located beneath the volcano, at depths down to 10 kilometres (6 miles) below the summit. The largest of these had a magnitude of 2.6.
“Some of them have been reported felt by people living in communities close to the volcano such as Fancy, Owia and Sandy Bay. At the present time the volcano-tectonic earthquakes continue, with the numbers of events fluctuating. “The very-small dome-extrusion events also continue,” NEMO said.