Decreased earthquake activity near Grindavik, magmatic intrusion just west of Mt. Thorbjorn, Iceland

Decreased earthquake activity near Grindavik, magmatic intrusion just west of Mt. Thorbjorn, Iceland

Earthquake activity near Mt. Thorbjorn, Grindavik has decreased over the past 6 days, but small earthquakes are still being detected.

Indications are that the crustal deformation pattern has changed, however, the uplift has slowed down. In total, the uplift is about 5 cm (2 inches) since January 21 when the crisis started.

The most likely explanation of the uplift and earthquake activity is that a magmatic intrusion is located at 3 to 5 km depth (1.8 - 3.1 miles) just west of Mount Thorbjorn, the Icelandic Meteorological Office (IMO) specialist noted at 07:35 UTC on February 11, 2020.  It was previously estimated to be at 3 - 9 km (1.8 - 5.6 miles).

"It is most likely that this activity will stop without an eruption," IMO said.

Similar volcanic crises in the country suggest that this might be a long-term event, for which changes can occur week after week without the possibility to anticipate with certainty if the activity is resolved, Scientific Advisory Board concluded at the meeting held February 6.

During the meeting, possible scenarios that could be triggered in the event of an eruption have been also considered. In the coming days, it will be assessed whether it is necessary to increase the number of monitoring stations in order to improve the capability to follow the evolution of the events.


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From February 3 to 9, IMO detected around 700 earthquakes, a few hundred less than last week when 1 300 earthquakes were detected.

The largest earthquake detected was M3.7 on February 9, by the Mt. Hengill. People felt the earthquake widley in the southwestern part of Iceland.

Small earthquakes are still being detected close to Grindavik, and around 400 earthquakes were detected there this week.

Around 15 earthquakes were detected in Myrdalsjokull and one in Hekla.

Geological summary

The Reykjanes volcanic system at the SW tip of the Reykjanes Peninsula, where the Mid-Atlantic Ridge rises above sea level, comprises a broad area of postglacial basaltic crater rows and small shield volcanoes.

The submarine Reykjaneshryggur volcanic system is contiguous with and is considered part of the Reykjanes volcanic system, which is the westernmost of a series of four closely-spaced en-echelon fissure systems that extend diagonally across the Reykjanes Peninsula.

Most of the subaerial part of the volcanic system (also known as the Reykjanes/Svartsengi volcanic system) is covered by Holocene lavas.

Subaerial eruptions have occurred in historical time during the 13th century at several locations on the NE-SW-trending fissure system, and numerous submarine eruptions at Reykjaneshryggur dating back to the 12th century have been observed during historical time, some of which have formed ephemeral islands.

Basaltic rocks of probable Holocene age have been recovered during dredging operations, and tephra deposits from earlier Holocene eruptions are preserved on the nearby Reykjanes Peninsula. (GVP)

Featured image credit: IMO

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