By Crispian Balmer
ROME (Reuters) - Central Italy is one of the most active earthquake zones in world, with tremors regularly shaking the country's mountainous backbone.
Most of the quakes are so negligible they are barely felt in the centuries-old communities that dot the landscape, registering only on electronic sensors. But on Wednesday a deadly tremor struck, killing at least 73 people and flattening hundreds of buildings.
With other such disasters seen as inevitable in the future, experts say Italy could do more to protect life and property.
"Italy can expect an earthquake with a magnitude above 6.3 every 15 years on average. That should encourage a greater culture of seismic prevention and civil protection," said Fabio Tortorici, head of studies at Italy's Geological Institute.
Wednesday's quake measured 6.2 and hit just 6 miles (10 km) beneath the surface of the earth, a shallow depth that multiplied its destructive force, according to the U.S. Geological Survey.
"The Apennine mountain belt which runs down the spine of Italy is gradually being stretched in a northeast-southwest direction by tectonic forces at a rate of around 3 mm (0.12 inches) per year," said Richard Walters, lecturer in Earth Sciences at Britain's Durham University.
"This slow stretching causes stress to build up in the earth's crust, which is then released in earthquakes just like this one," he said.
It was the most destructive such disaster in Italy since 2009, when a quake killed more than 300 people, left 55,000 homeless and devastated the 13th century city of L'Aquila.
That tragedy once again revealed the fragility of Italy's infrastructure, with both modern and ancient buildings, including churches, hospitals and a college dormitory in the area ravaged by the shaking earth.
A 2008 survey by civil protection experts said only 14 percent of buildings in the most vulnerable swathe of the country met seismic-safety standards.
That same year, new norms were brought in demanding a much higher standard of construction for new buildings, but that still left the vast majority of homes and offices exposed to seismic activity.
A report released last month by Italy's national insurance association said two-thirds of the country's municipalities were in earthquake zones, with a similar proportion of its buildings built without any earthquake protection.
"Some things have changed, but more could be done," the Geology Institute's Tortorici told Reuters.
"The real problem lies with properties built before the 1970s when there were zero earthquake norms. The country was covered in cement which has a very finite life," he said.
Any measures to strengthen older buildings across Italy and make them safer would meet fierce resistance given the huge cost of reinforcing every medieval hamlet and Renaissance palace without stripping them of their charm.
Tortorici said the government could offer incentives to encourage a nationwide safety drive. However, groaning under the biggest debt mountain in Europe, Italy can ill-afford generous enticements to the private sector, or the sort of massive investment needed to make all public buildings safe.
Surrounded by rubble in the village of Arquata di Tronto, 65-year-old Altiero Cinaglia sounded fatalistic about bringing Japanese-style safety standards to creaking Italy.
"What are we supposed to do? You can't tear down all the old buildings for new ones. These towns live for tourism in the summer time and tourists want to see the old beautiful buildings," he said. "There is nothing to be done."
(Additional reporting by Steve Scherer in Arquata di Tronto and Giulia Secreti in Rome; editing by Giles Elgood)