More than a week ago, a scientist little known in earthquake circles made a bold prediction of a destructive earthquake in the Abruzzo region of central Italy based on spikes in radon gas. Giampaolo Giuliani went so far as to tell the mayor of a town there that it would strike within the next 24 hours.
His deadline passed and for days, nothing happened.
Then, early Monday, a magnitude-6.3 earthquake struck near the town of L'Aquila, sparking a controversy around the world about whether Giuliani truly predicted the temblor or whether it was a fluke of timing.
"This happens all the time," said Tom Jordan, director of the Southern California Earthquake Center, who is also principal investigator on a worldwide project called the Collaboratory for the Study of Earthquake Predictability. "People send out predictions based on various stuff. It's always hard to evaluate."
The controversy around Giuliani is the latest twist in the maddening scientific quest to predict earthquakes. Over the decades, many ideas have been tested, including studies of cockroach activity along faults, ground warping and the movement of air masses.
"Being able to predict earthquakes is the Holy Grail of seismology," Caltech seismologist Egill Hauksson said. "The more we try, the less progress we seem to make."
In 1975, scientists thought the riddle had been solved. Chinese government officials detected foreshocks and successfully evacuated the area of Haicheng before a magnitude-7.3 earthquake. Unfortunately, authorities were not able to predict the Tangshan earthquake a year later, and several hundred thousand people died.
Researchers said most of the ideas over the years have been discredited, including the radon gas theory that Giuliani used when making his earthquake prediction in Italy.
Soviet scientists appear to have done the pioneering work in the radon field, correlating radon and thoron emissions in well water near Tashkent, Uzbekistan, in the 1960s to an earthquake in 1966. China and Japan also invested in radon research.
Interest in radon as an earthquake signal peaked in the 1970s in California, said Susan Hough, who serves as scientist in charge at the U.S. Geological Survey in Pasadena and is writing a book on earthquake prediction. In 1979, for instance, scientists at Caltech and other institutions said they found changes in gas levels in Southern California wells right before earthquakes in Malibu and Big Bear that year.
"The whole thing deflated when the places where they had detected [radon] had no earthquakes and earthquakes happened in different areas," Hough said.
Giuliani, who is a technician at Italy's well-respected National Institute of Nuclear Physics, appears to have spoken up about his radon data as early as March 24, in an interview on the Italian blog Donne Democratiche.
Warner Marzocchi, chief scientist at Italy's National Institute of Geophysics and Vulcanology, said he first heard about Giuliani's prediction around March 28, when the statements were broadcast on television and radio.
Residents of the Abruzzo region were already on edge because a series of small earthquakes had been rattling the area for weeks, mostly around a town called Sulmona, about 30 miles south of L'Aquila, Marzocchi said.
Giuliani told the mayor of Sulmona that a quake would strike in six to 24 hours, Marzocchi said.
The Italian Civil Protection Agency tried to downplay the predictions, but some residents of Sulmona evacuated, Marzocchi said. They had returned by the time the quake struck near L'Aquila, but there was no major damage in Sulmona, he said.
"It's impossible to give credit to him," he said. "Nothing happened for one week -- and in a different place!"
Giuliani's old-school predictions come at a time of progress in earthquake forecasting, after the disillusionment of the 1980s and '90s, Jordan said.
Technological improvements have allowed scientists to collect more data at fault lines and to generate complicated computer models based on reams of historical earthquake statistics, Jordan said.
"To show you're doing better than guessing requires some very careful testing procedures," he said. "We've got a whole series of models that are being formally tested in California to see if they do a better job of predicting earthquakes than other models."
The best models, he said, consider the whole cascade of foreshocks, main shocks and aftershocks. The group is preparing a scientific paper on its preliminary results, he said.
BEGIN TEXT OF INFOBOX
Rejected ways to tell a temblor
Here are some earthquake prediction ideas that have come and gone over the years.
* Gases: Releases of radon gas from the earth's crust before a quake occurs.
* Weather: Movement of air masses and pressure fronts are precursors to quakes.
* Earth movement: Bulges occur in the earth before a major temblor, based in part on the "Palmdale Bulge" of the 1970s.
Source: Susan Hough, U.S. Geological Survey