Seismic activity at La Soufrière, St Vincent changed significantly today when the seismic station closest to the summit began recording low level earthquakes on April 8.
Six separate episodes, or bands, of tremors starting at 3 a.m. were recorded with intervals of about two and a half hours between them. The quake episodes slowly increased in magnitude.A tremor is a continuous seismic signal usually associated with the movement of magma toward the surface.
The seismic network also recorded five long-lived earthquakes during the second and fourth quake bands. Long-lived earthquakes are also generally associated with the movement of magma.
There were also two brief swarms of small volcano-tectonic (VT) earthquakes, both occurring between bands of quakes. These were located at depths of up to 5 kilometers below the summit of Soufrière, which is consistent with the depths of the two VT swarms on March 23-26 and April 5.
High and continuous periods of gas evolution from the top of the volcano, coinciding with the tremor bands were observed. Sometimes there was a well-defined plume.
Visual observations from Belmont Observatory in the early evening indicate that the height of the dome has increased significantly during the day. The glow of the dome was visible from Belmont.
The volcano has entered a period of heightened activity indicating a new batch of magma near or approaching the surface. The possibility for the activity to go into an explosive phase has increased significantly. Based on current data, it is not possible to say exactly what the timescale would be.
NEMO Saint Vincent and the Grenadines
Soufrière de St. Vincent - 08.04.2021 / 21:57 - the incandescence is visible from Chateaubelair - Doc. UWI-SRC
Prime Minister Dr Ralph Gonsalves has issued an evacuation order with immediate effect.
The safety zones are North Union to Kingstown on the windward side of the island, Barouallie to Kingstown on the leeward side and the Grenadine Islands.
During the night of April 8-9, for residents of Fancy and above the river, evacuations began.
Sources : UWI-SRC & NEMO SVG
Map defining the evacuation zones - The earthquakes of 08.04 were felt in Fancy and Sandy bay - Doc. UWI-SRC
Soufriere de St. Vincent - thermal anomaly (selom Mirova between VRP28 and 52 MW on 04/08) - Sentinel-2 band image 12,11,8A of 04/08/2021 / 2:37 p.m. via Mounts project
La Soufriere Eruption 8th April- 2021. Climbing into the crater of an Eruption. - vidéo Island Vibes / https://youtu.be/XDMxTTS0G3U
Seismicity and inflation under the Piton de la Fournaise continue.
For the day of April 8, 2021, 48 earthquakes were recorded under the summit area. The GPS of the summit zone and in the far field record an ingflation, witness of the pressurization of a superficial and deep source
This recharging process observed since March 13, 2021 can last several days to several weeks.
Piton de La Fournaise - Illustration of the deformation between 09.02.2021 and 09.04.2021 -. The baselines (variation of distance between two GPS receivers) crossing the Piton de la Fournaise building, at the top (top), the base of the terminal cone (in the middle) and in the far field (bottom) are shown here. ) (see location on the associated maps). An increase is synonymous with elongation and therefore swelling of the volcano; conversely, a decrease is synonymous with contraction and therefore deflation of the volcano. Any periods colored in light pink correspond to eruptions. - OVPF
In Sinabung, in activity level 3 / siaga, the PVMBG provides information for April 8, 2021:
- 3 eruption earthquakes, with an amplitude of 22 to 33 mm, and the duration of the earthquake was 133 to 185 seconds.
- 1 earthquake related to a pyroclastic flow, with an amplitude of 120 mm and an earthquake duration of 216 seconds.
- 92 collapse / avalanche earthquakes, with an amplitude of 3 to 120 mm and a duration of 20 to 190 seconds of the earthquake.
- 8 blast / emission earthquakes, with an amplitude of 4 to 19 mm and the earthquake lasted 20 to 70 seconds.
- 13 low frequency earthquakes with an amplitude of 2 to 20 mm, and the duration of the earthquake was 10 to 34 seconds.
- 32 hybrid / multiphase earthquakes with an amplitude of 2 to 12 mm, the S-P was not observed and the earthquake lasted 5 to 20 seconds.
Seismicity has not changed much since early March.
Sources: PVMBG, Magma indonesia