Posted on behalf of Nicola Nosengo.
To Italian seismology experts, the earthquake that hit the Emilia region on 20 May, killing seven people, was yet another reminder that the country is very unprepared for seismic risks, despite being one the most earthquake-prone areas in Europe.
“Historical buildings are one thing. But it is unacceptable that modern constructions such as warehouses and industrial sheds have collapsed in an earthquake which was strong, but not exceptional,” says Stefano Gresta, president of Italy’s National Institute for Geophysics and Vulcanology (INGV). Although many historical buildings and churches were damaged by the earthquake (injuring about 50 people and forcing more than 5,000 out of their homes), five of the deaths occurred in small, recently built factories that completely collapsed, killing workers on night shifts. Had the earthquake occurred on a working day, those sheds would have been filled with workers, and the death toll would be much higher.
But with the main shocks reaching magnitude 5.9 (at 4:03 a.m. local time on 20 May), and 5.1 (at 15:18 the same day), the earthquake was not a terribly violent one. The L’Aquila earthquake, which killed 309 people on 6 April 2009, reached magnitude 6.3. “Let’s be honest, this was a small earthquake,” says Gian Michele Calvi, a professor of seismic engineering at the Institute of Superior Studies in Pavia, and president of the EUCENTRE Foundation (European Centre for Training and Research in Earthquake Engineering) in the same city.
Part of the problem is that the region around the epicentre of the quake (between the cities of Modena and Ferrara) is not as accustomed to earthquakes as in other parts of Italy, such as the north-east, Sicily, or the Apennine region (where L’Aquila is located). Until 2003, it was not even included in seismic-hazard maps. “The buildings which collapsed were mostly built before then, with no antiseismic measures at all,” says Calvi. “In such cases, prefabricated buildings such as sheds and supermarkets are more at risk than houses, because of their weak structure”.
In 2003, however, seismologists introduced a new map of seismic hazard across Italy, and the area of Sunday’s earthquake was reclassified as one of medium risk. “We were estimating a 10% probability of an earthquake of this kind in that area over the next 450 years,” says Gianluca Valensise, a research director at the INGV. “This earthquake was a rare event, but not a surprising one.”
Current maps of seismic risk in Italy, compiled by INGV scientists, are considered among the most accurate in the world, and form the basis of a 2006 law that imposes varying building standards according to each area’s risk level. Had those sheds complied with existing laws, says Valensise, they would not have collapsed. “But the application of that law has dragged on for years because of the high costs of complying with it, to the point that people were often formally authorized to circumvent it,” he says.
Calvi says that after the L’Aquila earthquake, the standards for new buildings have become stricter — in theory, at least — but few of the older ones have been adapted. “The most typical excuse is that small firms cannot afford it,” he says. “That is why the government should introduce financial incentives or tax exemptions for those who do it. Simply imposing the law and expecting people to comply will never work.”
What is most alarming, say the researchers, is that a relatively modest earthquake still managed to kill seven people in one of Italy’s wealthiest and best-run areas. A much stronger earthquake in the country’s southern regions, which combine higher seismic hazard with the lowest compliance with building standards, could prove to be far more devastating. The highest risk is in Calabria, the most southerly region of continental Italy, and in Sicily. In 1908, the cities of Messina and Reggio Calabria, on the opposite sides of the strait between Calabria and Sicily, were hit by a devastating 7.2 earthquake and tsunami, one of the most violent in Europe’s recent history. Should something of this scale happen again, says Calvi, “there would be tens of thousands of deaths”. And the main problem, according to Valensise, would not be the oldest buildings, which were built in the 1920s and 1930s following strict seismic codes, but rather post-war buildings that were completely unregulated because of corruption and illegal constructions.