Groundwater Radon Points to Dangerous Faults

Aug. 25, 2009 -- Spikes in the tiny amounts of radioactivity in groundwater may help scientists find dangerous hidden faults, or even indicate an impending earthquake, according to a new study.

Uranium is common in many rocks around the world. As it decays it leaves behind radon, among other by-products, which can escape into ground water or the atmosphere as a gas.

Now a team of researchers led by Alberto Gonzalez-Diez of the University of Cantabria in Spain are using radon to determine what faults may be ready to rupture, and to discover previously unknown danger zones. They've published their findings in the journal, Geomorphology.

Scientists have been tantalized for decades by hints of a connection between radon levels and quakes. Faults and small cracks in bedrock make way for water and gas to escape, they theorize. In areas where rocks routinely rupture during earthquakes, these fissures -- and the radon that dissolves out of the rocks -- should be more prevalent than elsewhere.

To test this relationship the team measured 47 natural springs in the north of Spain. Springs associated with known faults indeed had significantly larger concentrations of dissolved radon, they found. But they also found some springs had high radon but no known faults nearby.

Gonzalez-Diez believes the the high-radon springs are probably associated with previously unknown faults.

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Susan Hough of the United States Geological Survey said the method could be useful in the eastern and central United States, regions riddled with ancient faults -- many of them unmapped.

"The saying goes 'You've got faults without earthquakes and earthquakes without faults,'" she said. "The problem is there are lots of faults, but it's really hard to say which one will produce an earthquake."

Looking for radon spikes might help seismologists identify hidden, active faults that could be potentially dangerous.

But using this relationship to predict earthquakes has proven unreliable.

Some researchers have claimed to be able to predict earthquakes using radon. Last March, Italian scientist Giampaolo Guiliani caused a sensation when he cited measurements of radon gas to claim that an earthquake was imminent near the town of Sulmona.

A few weeks later, a magnitude 6.3 quake struck a few miles away, devastating the nearby city of L'Aquila and killing hundreds of people.

However, no one has ever been able to make consistent predictions. Gonzalez-Diez said that may one day be possible; for now his team is focusing his work on identifying previously unknown faults.

"We know there's a correlation between radon and earthquakes," he said, "but we're very far from being able to predict when an earthquake will occur."

Related Links:

United States Geological Survey

Discovery Earth

HowStuffWorks: Radon