An earthquake swarm continues to shake North Iceland, home to one of the world's largest and most active series of volcanoes. More than 800 quakes have rattled island residents, a number that's probably already out-of-date.
About 40 to 60 earthquakes hit every hour on April 2 and 3, according to the Iceland Geology Blog. Some smaller quakes preceded the biggest event, a magnitude 5.5 shaker that struck offshore Grimsey Island on April 2.
The latest swarm moved about 9 to 12 miles (15 to 20 kilometers) south of the biggest temblor, said Iceland's Meteorological Office. Another large quake, a magnitude 4.7, struck early this morning (April 4) in this southerly spot.
The earthquakes are scattered along the Tjörnes Fracture Zone, a north-south oriented transform fault that marks an offset along the Mid-Atlantic ridge. The Mid-Atlantic ridge is where new oceanic crust forms via the upwelling of magma.