Earthquake Risk Transfer for Iceland
Overview
The seismicity in Iceland is related to the Mid-Atlantic Plate boundary that crosses the country. Within the country, the boundary shifts eastward in the south and back toward the west in North Iceland through two complex fracture zones. The southern zone, called the South Iceland Seismic Zone, is located in the South Iceland lowland, while the other, the Tjörnes Fracture Zone, lies mostly off the northern coast of Iceland. The largest earthquakes in the country have occurred within these zones. Since A.D. 1700, 16 earthquakes of magnitudes greater than 6.0(Ms) have occurred in the the South Iceland Seismic Zone, and 9 earthquakes in the Tjörnes Fracture Zone. The maximum possible magnitude is estimated to be around 7.0(Mw) for both zones; this upper bound is caused by relatively low rock strength and thincrust in the earthquake zones. In the year 2000, two earthquakes (17 and 21 June) of magnitude 6.5(Mw) occurred in South Iceland. The highest recorded PGA in these quakes was 0.84g at the Thjórsá Bridge site.
On 29 May 2008, a 6.3(Mw) earthquake shook the area again. The distances between the epicenters of these three earthquakes are less than 35 km. These three events constitute an earthquake sequence, typical for the area. The last sequence before the 2000 and 2008 earthquakes occurred in 1896, when five earthquakes (Ms > 6) struck in the area, starting in the eastern part of the South Iceland Seismic Zone and migrating west during a two-week period, with the last major earthquake around the Selfoss farm (now a small town).