Italy: A History of Earthquakes

 Italy braces itself once again in the wake of a M 6.6 jolt that shattered the town of Norcia, in the Southeast of Umbria, causing major damage to the Monastery of St. Benedict, one of many Italian architectural jewels that are prone to seismic activity in the central part of the peninsula.

After the October 30th quake that rattled central ltaly between Marche and Umbria, only the façade of the stunning medieval Basilica has been left standing, as an eerie reminder of the sheer power of geological forces.

Italy, nested between the North and the South of Europe, stretching all the way from the Aps to the Mediterranean, has a long history of earthquakes.

Considering only the last 108 years, ten major, life-claiming events have hit the country: It all started with a devastating M 7.9 jolt and  subsequent tsunami on December 28th, 1908, when as many as 90,000 people lost their lives in Messina and Reggio Calabria, in the extreme south of the peninsula, a region that is regarded by geologists as the most dangerous in Italy in terms of the magnitude of future events.

The next deadly quake was in 1915 in Avezzano, Abruzzo, when 30,000 people perished in a M 7 seismic event that hit a land that would be stricken again, 94 years later, in April 2009.

In 1976 it was the turn of Northeast Italy to be rattled by a seismic sequence initiated by a 6.4 mainshock in Friuli, that killed almost 1,000 people.

On November 23, 1980, a major M 6.9 event crippled towns and villages in central Campania,  claiming almost 3000 lives.

In 1997 and 1998, the same area hit by yesterday’s temblor was affected by a long series of jolts, the most powerful of which was a M 6.1 that claimed 10 lives and caused the collapse of the roof of the Papal Basilica of Saint Francis of Assisi.

In October 2002, the town of S. Giuliano di Puglia (Molise Region) was shattered by a M 6 temblor that killed 27 children, as their primary school was reduced to rubble in seconds.

In 2009, it was the turn of Region of Abruzzo, almost 100 years after the Avezzano quake, to be ravaged once again by a seismic sequence that shook the town of L’Aquila from December 2008 until the mainshock of April 6th, when 309 people were killed and tens of thousands were left homeless.

In 2012, two back-to-back, M 6.0 quakes wrought havoc to the northern region of Emilia-Romagna, on May 20 and 29, claiming 27 lives.

The latest event prior to the October 30th quake in Norcia, was the 6.2 jolt that wiped out the town of Amatrice, in the Region Latium, not far away from the epicenter of the recentmost shock.

All the above attests, once again, to the fact that Italy is one of the most geologically active regions on Earth, as it is crushed between the European and African plate.

The opening of the southern Thyrrenian sea and the consequent rotation of central and southern Italy towards the Balcanian region is constantly producing movements along faults that are weakness areas in the crust along which the mighty geological stresses are periodically released.

Seismologists have long recognized that the release of stress along a fault can “pass on” stress to neighboring stuctures in the crust; this seems to clearly have been the case if we consider the October 30th event, that followed only 2 months after August 24th tremor in Amatrice.

However, also in the case of these so-called “clusters” of earthquakes, it is simply impossible, for any seismologist, to say in advance which fault will be he next to be activated.

Norcia had been able to withstand the Augut 24th event without major damage: This time, however, the town was at the very heart of the seismic crisis and one of the symbols of Catholicism, which had survived seven centuries of temblors, just couldn’t make it.

There’s one good news though: the most powerful earthquake in Italy in 36 years hasn’t claimed any lives; this is by no means a miracle, Saint Benedict has nothing to do with it: The simple fact is that Norcia was rebuilt to resist to earthquakes after the 90s seismic crisis, in compliance with seismic rules.

This should be a definitive wake-up call for Italian governors: The time has come to take major efforts to strengthen, once and for all, a country that is home to most of the world’s cultural heritage.

Federico Pasquaré Mariotto (Insubria University, Italy)