|ORIGIN TIME||01:36:33.1 UTC|
The Norcia earthquake of 24 August 2016 occurred in the central part of an earthquake belt that runs north-south through the Apennine Mountains along the spine of Italy. This area has been subject to destructive earthquakes throughout Italy's long history; an earthquake near Avezzano in 1915 (about 90 km south of today's earthquake) killed around 30,000 people and was one of the deadliest European earthquakes of the 20th Century. In 2009, a magnitude 6.2 earthquake in L'Aquila, 43 km south of Norcia, was one of the most damaging European earthquakes of recent years: over 300 people were killed, 1,500 injured and approximately 70,000 people were made homeless. In 1997, the Umbria-Marche earthquake sequence killed 11 people, injured approximately 100 people and caused extensive damage throughout the region. The epicentre of the Norcia earthquake is about 50 km south of the Umbria-Marche sequence.
The earthquake was felt throughout the Italian peninsula. There was severe ground shaking in the epicentral area, which can cause great damage to poorly built structures and there are many unreinforced brick and masonry buildings in the region that are vulnerable to earthquake shaking. The collapse of such buildings was found to be the greatest cause of death in the L'Aquila earthquake.
The earthquake occurred at a shallow depth (4km) on a NW-SE oriented fault, and the shallow depth contributed to the intense shaking at the surface. The underlying causes of earthquakes in the Appennine mountains are complex. Geological studies show that the earthquake faulting in the region results from what is called extensional tectonics, which is pulling apart the Earth's crust under the Apennine Chain. This is caused by the widening of the Tyrrhenian Basin, which lies between the mainland of Italy and Sardinia and Corsica. The mountains themselves are the result of ancient subduction of the Adria microplate, which lies to the east, under Italy. However, recent evidence suggests that this microplate may now be moving east. These two factors combined with the northwards movement of Africa into Europe, result in the complex tectonics in the region.
Updated 24 August 2016 16:00 UTC