Northern Italian Earthquake of May 2012 Has Complex Tectonic Setting

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Why Italy is Earthquake-Prone

Without direct information from seismological reports, it isn’t possible to say what the exact cause of the 2012 earthquake was. A glance at the tectonic map of the Mediterranean produced by the USGS following an M6.3 tremor which struck further south in the town of L’Aquila in 2009, however, indicates why earthquakes occur in that area in general.

L'aquila earthquake damage

Damage caused by the L'Aquila earthquake in 2009 Image courtesy of kremlin.ru)

Tectonically, the simplest explanation is that the Mediterranean region is caught between the African and Eurasian plates as they converge. A closer look shows a more complex situation. The USGS summarises it as “involving both subduction of the Adria micro-plate beneath the Apennines from east to west, continental collision between the Eurasia and Africa plates building the Alpine mountain belt further to the north and the opening of the Tyrrhenian basin to the west.

While discussing the cause of the 2009 earthquake, University of Chicago geologist Chris Rowan notes that although the overall context of the Mediterranean is one of compression, as the major plates move together, local extension of the crust in the Mediterranean to the west of Italy means that the rocks are extending, causing slippage along existing faults. It seems likely, therefore, that it is this movement which is responsible for the May 20 event.

Historic Earthquakes in Italy

Despite its tectonic instability, Italy isn’t among the most vulnerable of countries in terms of earthquakes, but it still experiences regular and damaging tremors. The USGS historic earthquakes list shows that the south and central areas of the country have experienced 12 events of M6.0 or greater, with three M7.0 or more.

Historically, earthquakes have caused significant loss of life in Italy, with estimates for five major events prior to 1920 suggesting a total loss of life in the region of a quarter of a million. Subsequently, casualty figures have been lower but remain significant, with over 300 people losing their lives to earthquakes in the country in the 21st century.

Sources

BBC News online. Italy quake homeless in emergency shelters. Accessed May 21, 2012.

Rowan, C. Tectonics of the Italian earthquake. Accessed May 21, 2012.

USGS Earthquake Hazards Program. Magnitude 6.0 – Northern Italy. Accessed May 21, 2012.

U.S. Department Of The Interior/USGS.  Summary Map M6.3 L’Aquila, Italy, Earthquake of 6 April 2009. Accessed May 21, 2012.

USGS. Historic Earthquakes listing. Accessed May 21, 2012.

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