Italy suffered many terrible earthquakes. In 1908, Messina's earthquake caused over 100 thousand deaths. In the 17th century, the earthquake in the Noto Valley (Terremoto della Val di Noto) caused 60 thousand deaths. A century later, an earthquake occurred on the Messina Strait causing 50 thousand victims. Then again, the number of earthquakes that occurred in the Abruzzo, Irpinia and Friuli areas of Italy have been so frequent, in history, that they are actually difficult to enumerate. Italy’s recent earthquakes are also difficult to forget: the Friuli one with 989 victims, the one in Irpinia with 2,914 victims, the Aquila one with 309 deaths, and the one in Amatrice with 299 victims.
Italy is one of those Mediterranean countries with the highest earthquake risk. Located in an area where the Eurasian and African plate meet, Italy's earthquake map presents a deep purple line with reddish contours, cutting right through the map’s center. In that area, especially, the structures built without anti-seismic principles, are at risk of collapsing. This is mainly because the walls of the buildings not built according to earthquake-resistance rules, are not adequately connected to the flooring. They collapse, making the garrets precipitate to the ground too. The first tremor shifts the foundations, shaking the lower floors, while oscillating the higher ones; the second tremor cracks the buildings open, as if built of fragile ice. This, on the contrary, does not happen with earthquake-resistant buildings. Their actual structure lets them move and shake without breaking.
Various studies lead to different results. In general, only 25% of Italian houses are designed and made with earthquake-resistant principles in mind. As the Chairman of the Italian Engineers Board Armando Zambrano said, Italy's structures "mainly include old historical heritage with buildings still made with rocks or materials that are not always resistant". There are obviously laws that require that new buildings abide by earthquake-resistance techniques and rules. The fact that Italy, in general, lacks an overall earthquake-resistance culture, causes the problem of the old existing buildings to be greatly overlooked, and eventual re-modernizations are always voluntary and costs are mainly to be paid by their owners. This insufficient attention towards the earthquake risk, is also demonstrated by the fact that there are very few owners who decide to insure their house against this type of damage: only 1% of buildings in Italy are insured for this purpose.
Two years ago, exactly, Giovanni Azzone, Milan's Polytechnic rector, was asked to estimate, how much it would cost to secure Italian structures against earthquakes. The result emerging from the study, which ranged widely, started from €36.8 billion to reach €850 billion. Many factors and variables must, in fact, be taken into consideration. Azzone, for example, calculated that €25 billion would be spent to apply the Sismabonus (earthquake premium) to Italy’s most endangered 648 municipalities. And this is just considering the buildings with load-bearing walls. If, instead, the number of municipalities were increased, to also include the reinforced concrete buildings built up to 1981, the estimated amount, would rise, in fact, to €850 billion.
It's also important to know that earthquake-resistant buildings do not cost excessively more compared to a normal structure, as there is usually just a 10% surplus price. These costs are needed to make houses more elastic, by using steel, a “more plastic” material. They also are needed to further reinforce the structure with reinforced concrete cages, and to position heatsinks and dampers, and all fundamental elements needed for earthquake-resistance purposes.
Since the Morandi Bridge collapsed, attention to safety in relation to Italian structures has moved a lot in the direction of large infrastructure. Only one out of four houses is built according to earthquake-resistance principles. And when this applies to infrastructure, the situation is not any better. In fact, as Strada dei Parchi Vice Chairman, Mauro Fabris, said "60% of Italy's infrastructure does not comply with earthquake-resistance regulations”. Fabris's analysis begins from two of the motorways that he manages: the A24 and the A25. Since October 2018, there's a heavy-vehicle transit limitation for 87 of its viaducts.
How can a motorway infrastructure meet and deal with an eventual earthquake risk? Public funds can radically be used to totally abandon viaducts at risk, modifying road routes, at a good extent. As for the A24 and A25 motorways, there has been a proposal suggesting that their viaducts be replaced with tunnels. The Italian Ministry of Transport, though, did not accept the proposal. So it was decided, instead, to proceed with restraining interventions, to improve the viaduct’s joints.
It must be noted that earthquake-resistance related issues do not only concern the A24 and A25 viaducts, nor just the motorway network. The Sente Viaduct, for example, a road bridge built between the two Italian regions Abruzzo and Molise, was closed last Autumn, because one of its pillars rotated, putting the viaduct's safety at risk, from a static engineering perspective, and not just from an earthquake-resistance one.
Bridges and viaducts are not the only infrastructure facing an earthquake risk. Tunnels are also among the infrastructure to analyse for seismic risks. These engineering works, in any case, are less critical, during earthquakes, compared to viaducts. It all depends from the type of rocks.