An intense earthquake swarm in Mt. Herðubreið in the NE Central Highlands shows no sign of slowing down. Nearly two hundred quakes have been detected just south of the volcano since the swarm began shortly after nine yesterday morning. At quarter to seven yesterday evening the Herðubreið swarm was joined by a 3.4 magnitude quake in the central caldera of the Bárðarbunga system.
The Icelandic Meteorological Office located the epicenter of the 3.4 magnitude Bárðarbunga quake at a depth of only 800 m (o.5 mi) in the NE part of the caldera. A second 3.6 magnitude quake was detected in the same area on Monday morning.
Geologists believe the seismic activity in Bárðarbunga is caused by the volcano refilling its magma chambers since the 2014-15 Holuhraun eruption.
Unexplained seismic activity at Mt. Herðubreið
However, the seismic activity of the STILL EXTINCT Herðubreið remains a mystery. Mt. Herðubreið, like all mountains in Iceland, is an extinct volcano, formed in a single eruption 10-11.000 years ago. It is located within the Askja volcano system, a very active system. The area, however, is known for high levels of seismic activity, including fissure rifting events.
The activity in Herðubreið began at 9:21 yesterday. It’s activity has been concentrated at a significant depth of a few kilometers just SW of Herðubreið. A high level of the quakes has been relatively powerful, 1+ on the Richter scale.
There are no signs of imminent volcanic activity geologists assure us.