A strong earthquake swarm offshore North Iceland
Three earthquakes recorded above M5.0
A strong earthquake swarm started
on 19th of June offshore North Iceland, NE of Siglufjörður. Three earthquakes
above M5.0 have occurred since the swarm started. On 20th of June a M5.4
earthquake occurred at 15:05 and a M5.6 at 19:26. Both these earthquakes were
located around 20 km NE of Siglufjörður. The largest earthquake of the swarm
occurred on 21st of June at 19:07 and was M5.8. It was located around 35 km NNE
of Siglufjörður.
The IMO received hundreds of felt reports from all over the
northern part of Iceland and even some from the capital area. Since the
activity started IMO‘s seismic network has automatically located over 2500
earthquakes, thereof the three aforementioned above M5.0 and nine earthquakes
ranging from M4.0 to M4.6. After the M5.4 event at 15:05
20th of June the Civil Protection‘s alert level was raised to uncertainty
stage.
The earthquakes are of tectonic
origin and located close to the junction of Húsavík-Flatey fault and
Eyjafjarðaráll graben which are part of the Tjörnes Fracture Zone (TFZ). A
strong earthquake swarm occurred last in this area in 2012-2013 and then four
earthquakes above M5.0 were measured.
An eyewitness photograph of one of the landslides that occurred in one of the earthquakes. The landslides occurred in places where there are steep slopes and
debris and landslides have taken place before. (Photo: Sigurgeir Haraldsson)
No damage on property 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 20th of June landslides and falling rocks were observed close to epicenter of the events. The landslides occurred in places where there are steep slopes and debris and landslides have taken place before. The Icelandic Coast Guard flew an observation flight in the area with staff members from the IMO to inspect unstable slopes and recent landslides on 21st of June.
Compared to previous earthquake swarms in the area it is expected that this swarm will continue during the coming days. 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.
