Earthquakes charted online

CAIRO, Ill. -- Not long after an earthquake shook this Southern Illinois town, Bobby Mayberry was on his computer telling the U.S. government about it.

"I wanted them to know I felt it here," he said. "It's important to help them study it."

What Mayberry did the morning of June 6 not only helped the government study that small, 4.0 magnitude quake -- which caused minor damage near its Blandville, Ky., epicenter -- but also brace for potentially bigger earthquakes in the future.

Mayberry logged onto a Web site operated by the U.S. Geological Survey that invites people to report it when they feel the ground shake, and to describe in detail what they saw and felt.

The information creates a nearly instant online map of an earthquake's intensity, letting scientists for the first time measure not just where a quake is centered and how strong it is, but how far away its tremors could be felt and other important indicators, said David Wald, a USGS seismologist who created the site.

The human input helps fill gaps in the country's high-tech earthquake measuring system, he said, particularly in regions such as the Midwest, where seismic equipment to measure earthquakes isn't as common as in the West.

That high-tech equipment gives scientists "enough information to say what the magnitude and epicenter is" in Midwest quakes, Wald said, "but not ... what the shaking was like here, here and here."

"The end goal is getting earthquake information out and understanding hazards ... to reduce our losses down the road," he said.

When people in any state think they feel a quake, they can log onto the USGS earthquake site, click on "Did You Feel It?" report their ZIP code and answer a list of questions.

Did things fall from shelves, or did pictures just wiggle on walls? Was the shaking strong enough to wake the person up, or did the person sleep through it? Did big appliances tip over? Was the house cracked? If so, was it made of brick or wood?

The answers help scientists chart the impact of earthquakes and also determine things about them they wouldn't know otherwise, Wald said.

Scientists could see from the 231 reports the Web site took after the Blandville, Ky., quake that its intensity eased relatively close to its epicenter, indicating the earthquake originated from a shallow spot underground, Wald said.

Anyone viewing the site could also see four people from Jackson, Tenn., also felt it, as well as people from five different ZIP codes in Louisville, Ky., one person in Cincinnati, and dozens of others.

The large number of responses serves as a safeguard against prank reports, Wald said.

Getting input from many sources validates the information, says Mike Janssen, a weather anchor for WSIL-TV in Carterville.

"It's great whenever you can get folks from different areas on the same page talking about the same thing but from different angles," Janssen said.

The site, which was expanded from a California program, has been operating four years. But Wald said only recently has he seen the number of participants soar in areas such as the Midwest and South, where quakes are not too common.

The site got more than 17,000 reports after a quake rattled northeast Alabama on April 29, he said. It got about 6,700 reports after a quake shook Evansville, Ind., in June 2002.

Wald hopes it will lead people to pay more attention to how their buildings are constructed and other precautions they could take.

"This can lead to better decisions by people and legislators," he said, to prepare for the worst before it happens.

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On the Net:

U.S. Geological Survey: www.earthquake.usgs.gov