Wednesday, 25 January 2012

Earthquakes shake northern Italy.

At about 0.55 am on Wednesday 25 January 2012 local time (23.55 pm on Tuesday 24 January GMT) an Earthquake measuring 4 on the Richter Scale hit Italy about 10 km north of Verona at a depth of about 6 km, according to the United States Geological Survey. This was followed at about 9.05 am (8.05 am GMT) by a quake 4 km northwest of Castelnono di Sotto (between Palma and Viadana), that was measured as 5.1 on the Richter Scale at a depth of 10.2 km by the United States Geological Survey and 4.9 on the Richter Scale at a depth of 33 km by the Centre Seismologique Euro-Méditeranéen. This is quite a difference in depth and scale; since the quake seems to have been quite widely felt at the surface, the USGS estimate is probably more accurate.
Map showing the location of the two quakes, from the United States Geological Survey. The second quake is the larger square.

There are no reports of any casualties or damage at the current time, but reports of buildings being shaken by the quake and people running into the streets from Verona, through Milan and Turin to Genoa have appeared in the European press.

Italy is caught in the boundary between the Eurasian and African Plates. The east of the country sits on its own microplate, the Adriatic or Apulian, that broke away from Africa during the Cretaceous, and is now being pushed into the Eurasian Plate by the northward movement of Africa. To the southeast the Agean Sea Plate, under Greece, Anatolian Plate, under Turkey, and Arabian Plate, under Arabia, are suffering similar fates.

At the southern margin of the Adriatic Plate the last remnants of the oceanic crust that separated Africa from Italy are being subducted beneath the Adriatic Plate, giving rise to the volcanoes of Sicily and Southern Italy as the Earth's interior partially melts the sinking crust and the liquid rock rises to the surface as magma.

An eruption on Mount Etna, Sicily on 6 January 2012.

To the north the Adriatic Plate is being pushed into Eurasia, causing the two plates to crumple and forming the Alps and Apennine Mountains through the resultant uplift. This is not a gradual process, but happens in stops and starts as pressure builds up and is released, leading to Earthquakes. Occasionally these are severe enough to cause severe problems. The last major Earthquake in Italy struck L'Aquila in the central part of the country in 2009, killing 308 people and making about 40 000 homeless.

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