Background: Italy and earthquakes

With geological faults running up its spine, Italy is prone to earthquakes – although rarely as destructive as in Abruzzo today

Today's earthquake in the Abruzzo region of Italy was triggered by slippage in a faultline that runs north-south beneath the Apennine mountains.

There are geological faults, or weaknesses in the Earth's crust, all the way up the spine of Italy, and tectonic movement is very slowly pulling the crust, and the Apennine mountain range, apart.

The faultline is thought to be tens of miles long. The earthquake was so destructive because it happened at the relatively shallow depth of 6.2 miles (10km).

Italy is one of the most seismically active countries in Europe. The Alps in the north are the result of the African tectonic plate pushing north into the Eurasian plate, a process that continues at a pace of 3cm a year.

Movement of a second microplate beneath the Adriatic sea off the country's east coast is thought to have contributed to today's earthquake.

"On the basis of past seismicity in this area, the possibility of a further event of similar magnitude cannot be ruled out," said Roger Musson, a seismologist at the British Geological Survey.

Minor tremors are common in Italy, but it is unusual for the country to experience an earthquake as deadly as today's.

In 2002, a quake in the southern town of San Giuliano di Puglia killed more than 25 people, the highest number to die in an Italian earthquake in more than 20 years. More than 40,000 people lost their homes.

In 1980, more than 2,700 people were killed and several thousand injured in a quake measuring at least magnitude 6.9. The epicentre was at Eboli, about 50 miles south of Naples.

One of Italy's most deadly earthquakes struck a century ago in 1908, destroying the Sicilian town of Messina and, according to some estimates, killed as many as 100,000 people.

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