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Can radon gas leaks predict earthquakes?

An Italian researcher says he predicted Monday's quake. Is his claim credible?

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When asked about the value of these potential predictors today, he says that the theory behind them still hasn't been proved or disproved. "There are so few measurements made that there's not a good database to say, 'Oh, yeah, this works,' or 'it doesn't,' " says Dr. Scholz.

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One instance of a claimed success, as in the Abruzzo case, doesn't represent a reliable, repeatable result. To confirm that it works (among other problems), "you have to know by some other means when and where an earthquake will strike," says Scholz, in order to set out the instruments that can take the needed measurements.

In his March 23 interview, Giuliani said that more detectors were needed to create a network that "would allow us to monitor carefully radon activity."

Radon appears to have successfully presaged a quake in some instances, but not in others.

Even in China, where seismologists successfully used groundwater changes, animal behavior, and swarms of foreshocks to predict a quake in 1975, they were unable to foretell another devastating quake a year later, Dr. Waldhauser says.

And for all that seismologists have learned about earthquake processes over the past several decades, faults often still confound them.

Scholz cites all the attention paid to the northern end of the section of the San Andreas fault near Parkfield, Calif. Scientists seeded the area with sensors and drilled a bore hole deep into the fault to monitor conditions there. The earthquake originally predicted for 1998 came in 2004 – at the southern end of the segment, far from where the instruments had been placed.

"That's the way it goes in this business," he says.

Scholz says he holds out hope that his theory will get a more rigorous test as major earthquake zones become more heavily instrumented.

Still, "predicting earthquakes is the Holy Grail of seismology," adds Waldhauser. He notes that the Greeks are working extensively with measurements of fluid electrical properties as warning indicators.

Researchers in India, Japan, and elsewhere are continuing to probe the radon approach.

Some scientists are even looking at satellite measurements of small disturbances in the ionosphere – found through minute changes in the properties of radio waves at very low and extremely low frequencies – for potential warning signs.

But these days, seismologists – including those who continue to test the approaches Scholz and his colleagues first proposed – are doing well to provide forecasts, rather than predictions.

The forecasts, based on combing the historical records as well as digging trenches across faults themselves to build a history of temblors on a fault segment, sound more like an area weather forecasts. And they read like this, from the latest assessment by the US Geological Survey:

The USGS and other scientists conclude that there is a 62 percent probability of at least one quake of magnitude-6.7 or greater, capable of causing widespread damage, striking the San Francisco Bay region before 2032.