Italy earthquake: All you need to know.

Powerful earthquakes like the 6.2-magnitude temblor that rocked central Italy early this morning (Aug. 24) are surprisingly common in the region, geologists say.

The shaking was caused by movement in the Tyrrhenian Basin, a seismically active area beneath the Mediterranean Sea. Here, the ground is actually spreading apart, said Julie Dutton, a geophysicist with the U.S. Geological Survey. The same underlying geology was responsible for the devastating 2009 earthquake in the city of L'Aquila, just 34 miles (55 kilometers) away from today’s quake. That earthquake killed more than 300 people.

"It's a pretty complicated or complex area for earthquakes," Dutton told Live Science. "In this area, they have sizable earthquakes that cause destruction every so many years." [Photos of This Millennium's Most Destructive Earthquakes]

COMPLEX DAMAGING GEOLOGY

The epicenter of today's quake, which hit around 3:30 a.m. local time, was about 6.2 miles (10 km) southeast of the historic tourist town of Norcia. The earthquake killed at least 73 people and turned scores of charming medieval buildings into rubble. The shaking was felt all the way in Rome, about 70 miles (112 km) southwest of the city.

The temblor was caused by complicated geology. In northeastern Italy, the slow-motion collision of the African and Eurasian plates has pushed up the ground beneath the Alps. In fact, many of the quakes have occurred in towns fringing the Appenine Mountains, along the northeastern coast of Italy.

However, the quakes themselves are not caused directly by this uplift process. Instead, because the continental plate collision zone is drifting southeast, it is stretching the crust beneath a region of the Mediterranean Sea. This ground extension, which occurs at a 90-degree angle relative to the mountain range, is what was behind both the current earthquake and the 2009 L'Aquila temblor, Dutton said.

"It's a normal fault earthquake and it's an expression of the east-west extensional tectonics where the Tyrrhenian Basin is being opened up," Dutton said. Normal faults occur when the ground on one side of the fault slides down relative to the other side, and the motion goes in the direction expected based on the pull of gravity on the Earth, according to the U.S. Geological Survey.

This region is no stranger to ground shaking. In 2009, the 6.3-magnitude-6.3 that struck L'Aquila led to a trial in which the seismologists in the area were convicted of manslaughter for failing to predict the quake. (The guilty verdict against the scientists was later overturned.) In 1997, a 6.0-magnitude earthquake killed more than 100 people and damaged 80,000 homes. And records going back nearly 700 years document terrifying earthquakes in central Italy that caused people to abandon towns during the Middle Ages. 

The Telegraph, reporting on the I'll fated experience said thus:
Matteo Renzi, the Italian Prime Minister, has said at least 120 people have been killed by the earthquake that struck Italy in the early hours of Wednesday morning.

"This is not a final toll," Mr Renzi said after visiting  rescue workers at the centre of the earthquake zone in central Italy. Earlier the death toll from the quake had been put at 73.

Mr Renzi thanked rescuers for their efforts in recovering dozens of people from rubble caused by a massive earthquake in the region.

"At moments of trouble Italy knows how to cope. No family, no city, no hamlet will be left alone," he said.

The 6.2 magnitude quake, which sent residents fleeing their homes and running into the streets, is Italy's deadliest since a 2009 quake in the same area. A family of four were also trapped under the rubble and showing no signs of life.

The shallow quake, estimated to have struck after 3:30am at a depth of six miles, was felt across a broad section of central Italy, including the capital Rome where people in homes in the historic centre felt a long swaying followed by aftershocks.

The mayor of Amatrice near Rieti, Sergio Perozzi, told state-run RAI Radio 1 that there were downed buildings in the town centre and that the lights had gone out. He said he was unable to get in touch with emergency responders or reach the hospital.

"What can I tell you? It's a tragedy," he said. "Half the town is gone. There are people under the rubble... There's been a landslide and a bridge might collapse."

A resident of the Rieti region, which is between Rome and the epicentre of the quake, told the Rainews24 channel that she and most of her neighbours had come out onto the street after feeling "very strong shaking."

The European Mediterranean Seismological Centre put the magnitude at 6.1. The US Geological Survey put the magnitude at 6.2, with the epicenter at Norcia, about 105 miles northwest of Rome.

In 2009 a 6.3-magnitude earthquake in the Aquila region, which was also felt in the Italian capital, left more than 300 dead.

Italy is often shaken by earthquakes. Another quake hit the northern Emilia Romagna region in May 2012, when two violent shocks 10 days apart left 23 people dead and 14,000 others homeless.