Intense earthquake swarm at Tjörnes Fracture Zone, Iceland

An intense earthquake swarm is taking place at Tjörnes Fracture Zone volcano near Grimsey island, Iceland over the past 7 days. More than 1 100 of earthquakes were detected in this region since Wednesday, February 14, 2018. The last known eruption of this submarine volcano was in 1868.

The largest earthquake so far was M4.1 at 19:37 UTC on February 15, about 10 km (6.2 miles) ENE of Grimsey. "It is the largest earthquake detected in the seismic swarm that began a week ago and is still ongoing," the Icelandic Met Office said late Thursday. EMSC registered this quake as M3.7 at a depth of 14 km (8.7 miles).

A magnitude 3.2 earthquake occurred at 19:28 UTC in the same area, followed by two events above M3, at 19:38 and 19:39 UTC.

There are no signs of volcanic unrest, IMO said. "This area is part of the Tjörnes Fracture Zone and earthquake swarms are common in the area."

More earthquakes, even bigger, cannot be ruled out, the agency added.

A total of 1 165 earthquakes were detected since 08:56 UTC on February 14. 11 of them had magnitudes above 3, 162 between 2 and 3, 951 between 1 and 2 and 41 less than 1.

Tjörnes fracture zone earthquakes February 14 – 16, 2018. Credit: IMO

Regional seismicity

Geological summary

The offshore Tjörnes Fracture Zone is an oblique transform zone that separates the northern volcanic zone of Iceland from the Kolbeinsey Ridge, part of the Mid-Atlantic Ridge north of Iceland. 

A submarine eruption was reported during 1867-1868 at the SE part of the fissure system off the northern coast of Iceland along the Manareyjar Ridge immediately north of Manareyjar Island.

Featured image: Location of earthquakes at Tjörnes fracture zone – February 2018. Credit: EMSC