Very intense earthquake swarm shaking Reykjanes Peninsula, Iceland

A very intense earthquake swarm started close to Fagradalsfjall in Reykjanes Peninsula, Iceland on the morning of February 24, 2021.

The strongest in the sequence so far was M5.7, 3 km (1.8 miles) SSW of Keilir at 10:05 UTC, followed by numerous aftershocks. The quake was felt in many parts of the country, including in Húnaþing, Ólafsvík, Ísafjörður, and Hella.

All quakes are taking place at shallow depths up to 3.5 km (2.1 miles).

The Icelandic Met Office (IMO) is advising people to avoid steep terrain as rocks and boulders can fall and chances of landslides are increased.

IMO said more information will be available when the activity is further reviewed and encouraged people to familiarize themselves with the defenses and preparedness on the civil defense website.

The sequence started a couple of days ago and intensified on February 24 – with as many as 500 earthquakes from 00:00 to 11:36 UTC. 

A total of 11 earthquakes with magnitudes above 4.0 were recorded, IMO said.

USGS registered the strongest quake as M5.6 at a depth of 10 km (6.2 miles) and issued a Yellow alert for economic losses.

An estimated 3 000 people felt very strong shaking, 5 000 strong, 28 000 moderate, and 243 000 light.

 Read more: 

• Large-scale volcano-tectonic reactivation event in the Reykjanes peninsula, satellites map surface deformation, Iceland (Published July 24, 2020)
• M5.6 earthquake hits Reykjanes peninsula, the largest since 2003, Iceland (Published October 21, 2020)
• TW Tag: Reykjanes peninsula

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 13^th century at several locations on the NE-SW-trending fissure system, and numerous submarine eruptions at Reykjaneshryggur dating back to the 12^th 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