Rome wasn't built in a day, but many Romans feared it might be destroyed in one — on May 11, 2011.

The Italian capital was gripped by a psychosis over a purported prediction by a now-dead seismologist that a devastating temblor would strike the city Wednesday. Even as seismologists and officials including the mayor sought to reassure residents and stress that earthquakes cannot be predicted, the quake myth took on a life of its own in viral rumor-mongering on the Internet.

Spurred by superstition, some Romans left town just in case. The consumer group Aduc estimated that 20 percent of Romans did not go to work. And an agriculture lobby group said a survey of farm-hotels outside the capital indicated some superstitious Romans had headed to the countryside for the day.

Many storefronts were shuttered, for example, in a neighborhood of Chinese-owned shops near the city's central train station. A man in a coffee bar that did stay open in the neighborhood donned a construction worker's helmet as he served morning cappuccinos and croissants, the ANSA news agency said.

By sundown, the fears had not materialized. Instead, two quakes hit another Mediterranean nation, Spain.

The psychosis was based on a purported prediction of a major Roman quake Wednesday attributed to self-taught seismologist Raffaele Bendandi, who died in 1979. However, Paola Lagorio, president of the association in charge of Bendandi's documentation, says there's no evidence Bendandi ever made such a precise prediction.

But that doesn't even matter. The purported prediction has been the subject of Internet blogging, radio shows and dinner conversations alike for months now, many apparently faithful to an old Italian saying that goes, "It's not true, but I believe it."

"Some Roman citizens believed it the same way one can believe wizards, witches and stargazers," said Aduc's secretary Primo Mastrantoni.

The Rome quake prediction has often been mentioned alongside prediction of an apocalypse in 2012, with doomsday theorists citing the Mayan calendar and rare astronomical alignments.

David Schaefer, an author and expert on urban legends, said the Italian earthquake myth qualifies more like a panic than an urban legend.

"Urban legends are often quite innocent — they involve people scaring each other, but no one actually changes their behavior," he said. "Panics can be dangerous. The mechanics of panic are studied in riot control, and in things like stadium disasters where something sets off a crowd that then start moving in one direction for no clear reason."

Still, there was no exodus from the city, and many Romans stayed put. "Rome is Rome, you cannot question that. In Rome you don't die underground," said Enrico Cocchi, a proud resident of the city.

Italian officials have taken extraordinary measures to try to calm nerves and debunk the myth.

The country's Civil Protection department posted information on its website stressing that quakes can't be predicted and that Rome isn't particularly at risk. Toll-free numbers were set aside at city hall to field questions, which came by the hundreds, mostly from people asking at what time the quake would strike, ANSA said.

And the national geophysics institute said it had drawn more than 1,000 people as it opened its doors to the public to inform the curious and the concerned about seismology. In particular, the room where seisms are monitored has been full throughout the day, spokeswoman Concetta Nostro said.

By late afternoon, about 30 earthquakes had struck Italy, as is normal for this quake-prone country. But none in the Lazio region that includes Rome, Nostro said.

Mayor Gianni Alemanno called the myth "nonsense."

"Let's keep cool and let us not be easily impressed by chit-chat going around the web," he said. "It's a media thing." But, Alemanno added, "like any other city, Rome must be ready to cope with any kind of event or tragedy. A quake can take place any time, any city."

Seismologists have long stressed that no one can scientifically predict an earthquake, though they note that in quake-prone areas preventive measures can be taken, such as constructing buildings according to anti-seismic norms.

But that doesn't stop the rumors.

When the last big quake hit Italy — a temblor that struck the central city of L'Aquila and killed about 300 people in 2009 — controversy swirled around a researcher who claimed he had forecast it but was muzzled by authorities. Scientists have dismissed his theory based on measuring the amount of radon gas released by the earth.

As a devastating quake hit Haiti in January, there was an Internet and radio rumor that had people in Ghana sleeping on their rooftops thinking that a quake was about to hit there, too.


Nicole Winfield in Rome and Meera Selva in London contributed to this report.