Volcano-tectonic earthquakes being recorded at La Soufriere

Scientists at the Belmont Observatory, led by scientists from The UWI Seismic Research Centre (UWI-SRC), have noted a change in seismic activity associated with the ongoing eruption of the La Soufrière Volcano.

At present, the monitoring network is recording volcano-tectonic (VT) earthquakes, which began at 4:53 pm on Tuesday, March 23 2021.

“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 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 communities close to the volcano such as Fancy Owia and Sandy Bay,” a release from the National Emergency Management Organization (NEMO) said.

The release said that prior to yesterday, March 23, “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.

“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. These events were probably associated with magma movement beneath the dome, although their depth cannot be determined.”

That was the first time that such a swarm has been seen since the seismic network was upgraded in early 2021, the release said.

At the present time the volcano-tectonic earthquakes continue, with the numbers of events fluctuating. The very-small dome-extrusion events also continue.

“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.

“The La Soufrière Volcano continues to be closely monitored by a locally based team consisting of scientists from the Soufriere Monitoring Unit (SMU), The UWI Seismic Research Centre (SRC) and the Montserrat Volcano Observatory (MVO). This team work closely with an extended group based at the SRC (Trinidad) and MVO (Montserrat). The Team Lead at this time is Vincentian Professor Richard Robertson. The monitoring network uses a variety of techniques to monitor the volcano that are constantly being improved and upgraded.