Earth’s crust un­der stress

Daily Mirror - - NEWS -

THE quake in Nor­cia was in a shal­low fault in the Apen­nines, the moun­tain chain back­bone of Italy’s “boot”.

The tremor hap­pened at a depth of 6.2 miles on a fault that runs from the north west to the south east. And the epi­cen­tre was in the moun­tains just 6.2 miles to the south east of Nor­cia.

It was caused by the stretch­ing of the Earth’s crust as tec­tonic plates be­neath moved apart. Since the late Miocene era, a basin has been open­ing un­der the Mediter­ranean Sea where the Eurasian and African plates meet. The African plate is driven un­der the Eurasian – but the bend in the African plate can move back­wards in a process called “roll­back”.

Richard Wal­ters of Durham Univer­sity said: “The Apen­nine belt is be­ing stretched at a rate of 3mm per year. This causes stress to build up in the crust, which is re­leased in quakes like this one.”

Yes­ter­day’s was the most de­struc­tive tremor in Italy since one in 2009 that killed 300 and left 55,000 home­less.

Fabio Tor­torici of Italy’s Ge­o­log­i­cal In­sti­tute said: “Italy can ex­pect a 6.3 quake ev­ery 15 years on av­er­age.”

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