Intense earthquake swarm contines at Tjörnes Fracture Zone, Iceland

An intense earthquake swarm started on June 19, 2020, off the coast of North Iceland, NE of Siglufjörður. By 08:19 UTC on June 26, the Icelandic Met Office (IMO) has located over 7 000 earthquakes. The swarm is taking place on the Tjörnes Fracture Zone — an oblique transform zone that separates the northern volcanic zone of Iceland from the Kolbeinsey Ridge.

Three quakes over M5 have been detected, with the largest M5.8 on June 21, 34 km (21 miles) NNE of Siglufjörður. The two others are M5.4 and M5.6 on June 20, both located around 20 km (12.4 miles) NE of Siglufjörður.

Many smaller earthquakes are still being measured in the area, and more large earthquakes are likely to occur, IMO said on June 26.

No property damage has been observed in relation to the largest earthquakes but there were reports on smaller items falling from shelves. Following the M5.4 and M5.6 earthquakes on June 20, landslides and falling rocks were observed close to the epicenter of the events. The landslides occurred in places where there are steep slopes and debris and landslides have taken place before.

Compared to previous earthquake swarms in the area it is expected that this swarm will continue during the coming days, IMO said on June 22.

Previously earthquake swarms like this one have triggered a larger earthquake in the area. Therefore it cannot be excluded that a larger earthquake (>M6) can occur there, but in most cases, activity like this ends without a larger event than already has occurred.

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 credit: Google, TW.