SCIENTISTS HAVE NOTED A CHANGE IN SEISMIC ACTIVITY ASSOCIATED WITH THE ONGOING ERUPTION OF THE LA SOUFRIÈRE VOLCANO
(By Ernesto Cooke) – Geologist Professor Richard Robertson says that earthquakes currently taking place at La Soufriere is an indication that magma is trying to reach the surface.
Robertson on Wednesday evening said they are keeping a close eye on the situation as it could be indicative of something changing, such as, is it going to move from effusive to explosive.
“So far, magma is getting to the surface because an eruption is ongoing. However, there are pockets of magma leftover from the 79 eruptions; last year, something would have triggered the movement of that magma ”.
Robertson said what is happening with the volcano-tectonic (VT) earthquakes is an indication that more materials or magma deeper down is also trying to make its way to the surface.
Robertson further stated that there is a lot more resistance for it to come out because of the depth.
“ There are a lot more rocks on the magma, so for it to come to the surface, it has to build up more pressure and then push its way through, and when it does that, it breaks the rock, and that breakage sets off a seismic wave that our instrument detects as a VT event”.
(NEMO), The National Emergency Management Organisation on Wednesday 24th March said at 16:53 local time (20:53 UTC) on 23 March 2021, the monitoring network started recording volcano-tectonic (VT) earthquakes.
These earthquakes are normally associated with underground fractures of the rock mass and are commonly generated by magma pushing through an unyielding rock mass.
Unyielding: of a mass or structure not giving way to pressure; hard or solid.
The volcano-tectonic earthquakes were located beneath the volcano, at depths down to 10 km below the summit.
The largest of these had a magnitude of 2.6. Some of them have been reported felt by people living in North-Eastern communities close to the volcano such as Fancy Owia and Sandy Bay.
At the present time, NEMO says the volcano-tectonic earthquakes continue, with the numbers of events fluctuating. The very-small dome-extrusion events also continue.
Up until 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. These were almost always only recorded at the seismic station closest to the dome.
NEMO’s statement on Wednesday said 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. These events were probably associated with magma movement beneath the dome, although their depth cannot be determined.
This is the first time that such a swarm has been seen since the seismic network was upgraded in early 2021.
The National Emergency Management Organisation (NEMO) wishes to inform the public that earthquakes associated with the ongoing eruption of the La Soufrière Volcano continue to occur from time to time and some of the largest ones may be felt.
The alert level remains at Orange and no evacuation order or notice has been given. However, NEMO is encouraging residents especially person living in communities close to the volcano (i.e., the Red and Orange Volcanic Hazard zone), to heighten their preparedness in the event that it becomes necessary to evacuate at short notice.