May 12, 2011

Destructive Earthquake Strikes Spain, Leaves 8 Dead

A magnitude 5.2 earthquake in Lorca, Spain has killed eight people and left many more injured.

A magnitude five earthquake occurs somewhere in the world about three times a day, but Spain's buildings are not generally constructed to protect against quakes.

The Murcia region is the most seismically active in Spain, and some of the medieval buildings were badly damaged during the 5.2 earthquake.

This event occurred at just six miles below the Earth's surface.

Roger Musson from the British Geological Survey said it appears to have occurred along a fault line running from south-west to north-east.

Musson told BBC News the earthquake was caused by an oblique slip movement, which means that rocks moved sideways and upwards along the fault.

Seismologists reported that the 5.2 shock in Lorca was preceded by a magnitude 4.5 event about two hours earlier.

Maria Jose Jurado, a scientific investigator at the CSIC Institute of Earth Sciences, Jaume Albera de Barcelona, told a Spaniard newspaper that it was likely the area could also experience aftershocks in coming days.

Francisco Jodar, the mayor of Lorca, said as many as a third of Lorca's 90,000 residents spent the night outdoors after the earthquake in fear of aftershocks.

A military task force of 200 troops was sent to the area to provide aid and cordon off dangerous buildings.

Carla Vera, spokeswoman for the Red Cross in Spain, said about 15,000 people were left homeless in the city.

The Murcia fault line lies close to the subduction zone where Europe and Africa collide.  Musson said "most of the action is taking place off the coast of North Africa".

The energy released in these types of earthquakes comes from the expansion of the Atlantic Ocean floor at the Mid-Atlantic Ridge.  This expansion is pushing Europe in a south-easterly direction.

However, the eastern half of the Mediterranean is more seismically active than the west.

Musson told BBC that the eastern Mediterranean is more "tectonically complex," with movement occurring not just on the Eurasian and African tectonic plates, but also the Anatolian plate that encompasses most of the Turkey.

Several notable earthquakes have occurred along the Murcia fault in historic times. 

Less powerful earthquakes occurred in the area during the 1970s, but caused less damage.


Image Caption: Damaged train station in Lorca. Credit: Antonio Periago/Wikipedia (CC BY-SA 2.0)