Friday, August 26, 2016

"What makes Italy so frighteningly vulnerable to earthquakes"

From Quartz:
On the night of Aug. 24, a 6.0 earthquake destroyed the towns of Amatrice, Accumoli, and Pescara del Tronto in central Italy. It killed at least 268 people, injured hundreds, and severely damaged the homes of 2,500 people. Over 200 smaller quakes—a so-called earthquake swarm—have followed the main tremor, and are continuing to shake the area, adding further damage to the already tragic situation. Some of these are as strong as 4.2 on the Richter scale.

It was the largest seismic event to hit Italy since 2008, when a 6.3 quake struck L’Aquila—also in central Italy, along the Apennine mountain range—killing 308. Neither of these were isolated events: since 2000, well over 100 earthquakes of magnitude 4 or higher have occurred in Italy. And last century, earthquakes killed about 160,000 Italian civilians—more than both World Wars combined.

Every few years, a large earthquake strikes Italy, unleashing what’s now a sad routine: death, emergency rescues, thousands of people left without homes for years, rebuilding efforts, cities emptied of their souls. Politicians talk about implementing new policies that would prevent it from happening next time, but then the emergency is forgotten and nothing much changes—till the next quake hits.

Italy, compared to its European neighbors, is particular vulnerable to the devastation of earthquakes, due to a combination of three major risk factors: the country’s geodynamics, its architecture, and its culture.

A crash of plates
Seismic risk in Italy. (Photo courtesy of Protezione Civile Italiana)
Italy is at the point of contact of two large tectonic plates. It’s a geological situation that’s clearly visible: volcanoes dot the fault line in Sicily and the islands around it. The Eurasian plate, in the north, covers all of Europe and most of Asia (with the exception of the Arabian and Indian peninsulas). The African plate to the south covers Africa all the way to Antarctica.
About 30 million years ago, the African plate bumped into the European one, and birthed the Alps. At the same time, the Indian and Arabian plates pushed up against Europe; the interactions between these plates is the origin of the mountain ranges from the Pyrenees all the way to the Himalayas.
This movement hasn’t stopped since. It’s why the Alps—and the Himalayas—keep growing every year: the plates keep pushing against one another and forcing the mountain peaks higher and higher. It’s also the a main reason why large earthquakes are so common in Italy.
There’s also a a smaller fault line coinciding with the Apennine range, which starts northwest in Liguria where the Alps end and runs like a vertebral column down the center of the country for 1,200 km (745 miles) all the way to Calabria, in the very south.
Combined, these two fault lines put most of Italy at high or very high risk of large seismic events.
There are other European countries—Greece or Iceland, for instance—that share a relatively high likelihood of being hit by earthquakes,. But Italy’s development and population density makes it particularly vulnerable to high death tolls, especially since many of the highest-risk areas in the country are mountainous, which means ruinous landslides are common.

Earthquakes don’t kill people, buildings do
Geodynamics alone can’t justify the hundreds who’ve died in Italian quakes. Earthquakes of much higher intensity in populated areas of Japan, for instance, typically don’t cause the same death toll....MORE