There are have been nearly 200 earthquakes of magnitude 4.5 or greater since July. The greatest number were in New Zealand, Indonesia and Japan, but only three of these were classified by the US Geological Survey as having the maximum risk of fatalities and economic losses. All were in Italy.
Italy often hits the headlines for destructive earthquakes, but “in an international perspective, Italian earthquakes are small”, explains Gianluca Valensise, director of research at the Italian Institute of Seismology.
In the past century Japan, Chile and the Philippines were shaken by more than 10 earthquakes of magnitudes of 7 or greater, compared with two that struck Italy, in 1908 and 1915. Italy has not experienced any earthquake of 8+ compared to seven in Chile and 20 in the world.
The number of casualties from earthquakes in southern Europe show that these events tend to be much more destructive on the peninsula. Italy had fewer earthquakes rated 5+ than Turkey and Greece in the last century, but they caused at least double the number of fatalities.
So why do they cause so much damage?
More densely populated
Italy’s population density is more than double that of in Turkey and Greece and about 12 times that of New Zealand.
Moreover, in Italy a larger proportion of the population lives in rural areas, while the Greek and Turkish populations are more concentrated in urban centres.
This means that when an earthquake hits Italy, it is much more likely to affect a populated area than in Greece and Turkey.
A different type of quake — and right under Italians’ feet
Subduction earthquakes, caused by plate convergence, are much stronger, like the one in Japan in 2011 or in Chile in 1960, but their epicentre is usually in the oceans, far away from urban centres. These types of earthquakes are particularly dangerous for tall buildings, but not so much for one or two storey constructions.
On the other hand, most Italian earthquakes are of relatively small magnitude and these affect small buildings the most. They also happen right under the feet of the population. The riskier area is along the Apennines, a mountain range at the centre of the country.
Smaller magnitudes does not equate to smaller risk.
“Over a certain level of magnitude, usually between 5-5.6, the shaking itself does not increase, but a higher magnitude will spread to a wider area and will last for longer,” Dr Valensise told the FT.
Ageing architecture
When an earthquake does hit an Italian town or a city, it is likely to cause more damage because its buildings are old.
In Italy a significant proportion of houses — about one in 10 — is more than a century old and half of the housing stock was built before 1971, the year in which the first anti-seismic building regulation came into place for new residential properties and radical renovations.
However, that figure is the national average. In Amatrice, the town that was destroyed by the earthquake of August 24, 76 per cent of the housing stock was built before 1971. That number was even higher — 86 per cent — in the town of Accumoli, which is in ruins after the same quake.
Weak government oversight
Italy has an anti-seismic building regulation that assesses risk levels and provides technical guidance on how to build safer dwellings. But it is relatively new. The 1970s regulation excluded half of the country from the risk map. It was only in 2003 when a more accurate seismic map was adopted and only in 2009 when it was coupled with a comprehensive and up-to-date building regulation for new buildings and structural renovation.
To this day, there is no single regulation on existing buildings, largely because of the huge costs involved.
Despite that Norcia, a town near Perugia in the region of Umbria, went through a process of anti-seismic improvements on all its buildings because of its seismic history. During the earthquakes of August, the town registered very limited damage. Because Amatrice had been lucky in the past, its residents did not improve their dwellings in a similar way resulting in the disastrous outcome of the summer.
In comparison, in Japan there is a comprehensive anti-seismic regulation dating back to the 1920s, making the vast majority of housing stock in line with the regulation. “Regardless, when an earthquake does hit the land, it causes damages also in Japan,” adds Dr Valensise.
Bottom line? The government pays
In Italy, earthquake insurance is almost non-existent. Attempts to introduce it failed both because of the costs involved and because of the difficulties in assessing the risk.
“In order to insure a building against earthquakes we should know how houses are built. At the moment the risk premium would need to be assessed dwelling by dwelling, which is simply not feasible,” adds Dr Valensise.
This means the government is left with the responsibility of paying for the rebuilding costs. The Significant Earthquake database from the National Oceanic and Atmospheric Administration has not yet disclosed how much the reparations from this year’s earthquakes will cost, but estimates vary from $2.5bn to $16bn which is how much the l’Aquila earthquake of 2009 and the 2012 earthquake in Emilia Romagna ended up costing respectively.
This is certainly not good news for a country struggling to improve its fiscal balance and reduce its debt.
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