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Iceland Mag

Geology

Four powerful earthquakes since yesterday: Iceland's most isolated village, Grímsey island, trembles

By Staff

  • Earthquakes in the past 48 hours Magnitude 3+ quakes are identified with green stars. The three quakes in Grímsey are at the top of the map, the quakes in Bárðarbunga at the bottom. Photo/Icelandic Meteorological Office

Updated: The earthquake swarm around Grímsey Island has continued since Friday. A fourth powerful magnitude 3.0 quake was detected on Saturday morning at 8:08. The swarm seems to be continuing, although it does show signs of decreasing. More than a hundred and twenty quakes have been detected around Grímsey in the past 48 hours.

Four powerful earthquakes, magnitude 3+ on the Richter scale, have shaken Iceland since yesterday afternoon. Three of the quakes were north of Grímsey island, Iceland's most remote settlement, a small island 40 km (25 mi) north of the north coast of Iceland, while one was in the giant volcano Bárðarbunga, located beneath Vatnajökull glacier. 

The 3.4 magnitude quake in Bárðarbunga at 2:42 this morning, comes on the heel's of a powerful 3.7 magnitude quake yesterday morning.

Read more: Quick primer on Bárðarbunga, Iceland's most powerful volcano

An earthquake swarm shakes isolated island

grimsey_map.jpg

Grimsey island A small island off the north coast of Iceland. Photo/Google Maps

The quakes north of Grímsey are part of a larger earthquakes swarm of nearly 60 quakes of varying sizes which began early afternoon yesterday. The first quake, a magnitude 2 quake was detected 2.8 km (1.7 mi) north-northwest of Grímsey at 13:25. Nine more quakes were detected in the next couple of hours, most north of the island, but also some to the south. 

Read more: Why the constant earthquakes? Iceland is slowly being torn apart

The first major quake, a powerful 3.9 magnitude quake was then detected at 16:25 in the afternoon. The quake was clearly felt in the small island. Residents who spoke to the local newspaper Morgunblaðið said that houses trembled, but that no structures had been damaged. The inhabitants of the island are "used to everything by now", he added. A number of afterquakes were detected immediately in the next few hours.

Two more powerful quakes were then detected after midnight. A 3.5 magnitude quake at 1:59 in the morning and then a third 3.0 magnitude quake, at minutes past two in the morning. Both quakes had an epicenter 3.3 km (2 mi) north-northwest of the island, although at slightly different depths. The first at a depth of 9.4 km (5.8 mi), the second at a depth of 9.8 km (6 mi). All of the quakes in the swarm have taken place at significant depths. In Iceland earthquakes closer to the surface are more common in volcanic systems, caused by the movement of magma, while deeper quakes are more common in fracture zones, caused by the release of energy caused by the movement of the tectonic plates. 

Icelandic geology, fracture zones, seismic activity

Icelandic geology The Tjörnes fracture zone, north of Iceland, is know for high seismic activity.

An area known for high seismic activity
The island lies on the Tjörnesbrotabelti, or Tjörnes rift zone, a highly active area. The area, which is part of the North Atlantic Ridge, is known for high geothermal activity and regular and significant seismic activity, caused by energy being released as the tectonic plates drift in opposite directions from one another. 

A seismologist at the Icelandic Meteorological Office told the National Broadcasting Service that the quakes followed a well known pattern for the area, and that there were no signs of volcanic activity associated with the quakes.

A small, isolated settlement
Grímsey is a small island. The surface area of the island is just 5.3 km2 (2 sq miles), with tall cliffs on all but its southern coast. It is the northernmost settlement in Iceland, located 40 km (25 miles) off the north coast of Iceland, and one of the northernmost parts of Iceland, straddling the Arctic Circle. Only Kolbeinsey, an uninhabited island, little more than a skerry, lies further north. The island, which has a population of some 90 people, is connected to the mainland by a ferry and air.

Historically the inhabitants of Grímsey have lived off fishing, but the island's economy has been facing tough times in the past years as commercial fishing has been moving to larger harbours along the North coast. Tourism has recently been growing in the island. Grímsey has large colonies of sea birds, including Puffins.

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