3 vital facts about Italy and earthquakes
August 25, 2016
A brief history of Italian quakes
Italy has experienced 125 "significant earthquakes" since 1900. Twelve of those earthquakes struck in the past 16 years. They range from a magnitude of 3.5 in 1973 to magnitude 7.9 in 1905. At magnitude 6.2, the earthquake on 24 August 2016 was the eighth strongest in the region since the turn of the last century. The 2009 L'Aquila quake measured 6.3. A US National Centers for Environmental Information database lists 318 significant earthquakes in Italy since 1450 BC, including one at Pompeii in 63 AD.
A meeting of tectonic plates
The US Geological Survey says the region around the earthquake's epicenter at Norcia is "tectonically and geologically complex." The quake resulted from a "shallow normal faulting" in the Central Apennines.
The Apennines is a mountain range running the length of Italy from north to south. It was formed due to a process known as "subduction," where tectonic plates collide. Now this very region is being torn apart.
One of the main complexities is the meeting - and parting - of the African and Eurasian plates. The Eurasia plate moves in a northeasterly direction at about 24 millimeters (about 1 inch) per year.
A housing issue
We often focus on the number of deaths caused by earthquakes - and it stands to reason. But the damage caused to buildings is often far greater in pure numbers. A September 1997 earthquake in Umbria and Marche killed between 11 and 14 people (depending on the source of information), injured 100 people, and destroyed 800,000 homes. It was part of the "Umbria-Marche Seismic Sequence," which involved eight shakes over two months.
The US Geological Survey says housing in central Italy ranges from "vulnerable" to "earthquake resistant." Vulnerable buildings tend to be made of unreinforced brick with mud and mid-rise non-ductile concrete frames. In Japan, a company called Air Danshin Systems has been working on houses that levitate during earthquakes to make them more resistant to damage. The house sits on a deflated airbag. When it detects a quake, air is pumped into the airbag, lifting the house about 3 centimeters above its concrete foundation. The system has been described as "airbag" housing. Well, whatever works.