Friday, January 27, 2017

Italy earthquakes: Why the country gets so many of them, and how to survive one

[Independent] Once again, Italy has been shaken by deadly earthquakes. Dozens of guests and staff at the Hotel Rigopiano in the Abruzzo region are missing after multiple quakes triggered a massive avalanche. The luxury hotel, in the shadow of the Gran Sasso mountain, was engulfed by snow and rubble. As the rescue and recovery continues, questions have been raised about the dangers in one of the most seismically active regions of Europe.
How many earthquakes have there been in Italy recently?
Dozens, but most of them have been of fairly modest magnitude. There have been three of greater than 6.0 magnitude on the moment magnitude scale (a more sophisticated version of the Richter scale). The events were on 24 August (6.2), 26 October (6.1) and 30 October (6.6). They have all happened in a relatively small area of central Italy, about halfway between Rome and the Adriatic port of Ancona. 
These most recent earthquakes have occurred in the Apennines, the mountain range that forms the central spine of the country. They are being pulled very slowly apart, but the earth’s crust in this region is riven with geological faults. Typically, the stresses gradually build and then release catastrophically.
Why is Italy so susceptible to earthquakes?
“Italy is one of the countries in the Mediterranean with the highest seismic risk,” says the Italian Civil Protection Department. The reason: the country lies where the African and Eurasian tectonic plates converge. They are moving together at a rate of 4-10mm a year.
“The highest seismicity is concentrated in the central-southern part of the peninsula, along the Apennine ridge, in Calabria and Sicily and in some northern areas, like Friuli, part of Veneto and western Liguria,” says Protezione Civile.
The US Geological Survey adds: “The region's tectonic activity cannot be simply explained by the collision of the Eurasia and Africa plates. It has been suggested that deeper lithospheric processes are controlling some of the deformation observed at the surface. Read More