The Ölfus Earthquake, May 2008
At about 1545 on Thursday 29 May 2008 an earthquake shook much of southern Iceland. With a local magnitude of around 6.3 on the Richter scale it was the most powerful ‘quake in Iceland for eight years; not since June 2000 has there been anything quite as large.
The epicentre was just southwest of Ingolfsfjall, a well known mountain and prominent landmark, and roughly half-way between the towns of Selfoss and Hveragerði. The seismic waves propagated from the earthquake’s focus which scientists think was some 5km deep and shook the two towns and surrounding countryside of Ölfus rather vigourously.
There were many reports of damage inside people’s homes: shelves fell to the floor, crockery was smashed, mirrors and light fittings broken, but thankfully there were no serious injuries. Several people did have treatment for minor injuries, mostly cuts and scrapes from trying to pick up broken glass. A series of aftershocks, some more than 4 on the Richter scale, continued through the night and much of the next few days. The map, taken from the excellent web site of Veðurstofa, shows the pattern of seismic activity that took place. The green stars mark tremors of more than 3 on the Richter scale whilst each dot indicates a discrete tremor of under 3 on the scale. The map was generated the day after the main 'quake.
Modern buildings in Iceland are designed to withstand shocks much more severe than this and remarkably little structural damage was caused. Some older buildings and farm outhouses were not so lucky and the authorities identified 30 or so buildings in need of urgent structural repairs. Some are so damaged that they will be demolished.
Immediately following the ‘quake the police closed several bridges in the area as a precaution whilst they were checked for any structural damage. They all soon reopened though one has had a weight limit imposed whilst repairs are undertaken. The roads themselves escaped remarkably unscathed with no serious damage though lots of small fissures and cracks appeared in some areas. Temporary repairs were soon completed.
Earthquakes are commonplace in Iceland. The country sits astride the Mid-Atlantic Ridge, a tectonic boundary separating the continents of Europe and North America. Scientists describe this as a divergent or constructive plate boundary as the two plates are moving apart. Research indicates that the average rate of growth exceeds two centimetres each year so earthquakes and volcanic activity are not unexpected. This means that crustal tensions are constantly being released and strain does not build up to extreme levels as in other parts of the world where catastrophic earthquakes sometimes occur. The Ölfus earthquake developed along a fault of the strike-slip kind. There are many misconceptions about earthquakes, seismic activity and the very much misunderstood Richter magnitude scale. The links refer you to Wikipedia for more detailed information.
These past few days have once again reinforced how important modern building regulations are when incidents such as this take place. Icelanders are by no means complacent about such events but at the same time do not over-react to the occurrence. For most people it’s very much business as usual as it is with the hotels and guesthouses that we use on our tours.