Local, state and federal officials will discuss geological maps and the easing of building code restrictions in earthquake-prone areas.
By Joe Walker email@example.com
At stake are high costs and work to make buildings more earthquake-resistant based on county-by-county U.S. Geological Survey maps that experts say are hard to interpret and donít take into account conditions unique to various regions.
Mapmakers and others attending the daylong workshop ó starting at 7:30 a.m. CST at the Holiday Inn North on Newtown Road ó will discuss what can be done to make the maps more practical, he said.
Meeting organizer John Kiefer, vice chairman of the Kentucky Governor's Council for Earthquake Risk Reduction, said the maps put the Paducah-area earthquake risk higher than the risk in California.
"We don't belong in that class," said Kiefer, assistant state geologist with the Kentucky Geological Survey in Lexington. "We know we've got a threat in Paducah, but we need to be realistic about it."
Kiefer's group has begun a state-funded seismic study designed to make the maps more specific to the Paducah area, which is in the New Madrid Fault zone. The findings could lessen the cost of construction generally and improve Paducah's chances of landing a 500-job gas centrifuge plant to enrich uranium.
Because tall centrifuge cylinders spin at high speed, they are very prone to shaking. A local nuclear energy task force is concerned about the potential added cost of making the plant earthquake resistant. Kiefer said representatives from USEC Inc., which will build the plant, and the Department of Energy are expected to attend the meeting.
"The meeting is very important to the centrifuge plant and the effects the maps are having on construction in our neck of the woods," said Ken Wheeler, head of the task force and chairman-elect of the Greater Paducah Economic Development Council.
Wheeler said he and McCracken County Administrator Steve Doolittle will be among the local officials at the workshop. Mark Caldwell of Apex Engineering in Calvert City is scheduled to speak Monday afternoon on seismic issues relative to stricter state building codes.
Caldwell, past president of the Structural Engineers Association of Kentucky, earlier called the maps ludicrous but said his group made suggestions to make the codes more user friendly, particularly as they relate to seismic standards.
The Kentucky Geological Survey is conducting a second study to test how soil would affect shock waves during a major earthquake. Crews have drilled an 825-foot-deep hole in the Sassafras Ridge area of south Fulton County and plan to install instruments before Christmas to read shock waves. The U.S. Geological Survey is paying $70,000 of the roughly $90,000 cost.
Landowner Austin Voorhees of Hickman allowed free access to his property, said project leader Ed Woolery, a senior researcher for the state survey. Woolery said the site was picked because it is central to the New Madrid Fault and normally has one or two very small tremors monthly.
"It has a relatively high rate of activity, so we're hoping to collect the most data in the shortest period," he said. "When Mother Nature provides us with an event, we will be able to do the calculations and that sort of thing in short order."
Woolery said he expects the results to confirm modeling data that suggest soil amplifies small tremors in the New Madrid Fault area but dampens larger earthquakes. The information will be valuable in reassessing the USGS seismic maps, which represent what occurs in bedrock but not in soil, he said.
"To be fair to the USGS, they're charged with a huge task to go out and prepare seismic hazard maps for the whole nation," Woolery said. "And they're trying to incorporate a lot of uncertainties."
New Madrid Fault bedrock is below more than 2,000 feet of soil and sediment, compared with California bedrock, which is near the surface. He said that makes mapping easier in California, where big quakes occur once or twice a century, and harder in western Kentucky, where an 1822-type tremor occurs every 500 to 700 years.
The USGS conducted blasts two weeks ago near Memphis, Tenn., that were 160 feet below ground and felt by instruments 31 miles away. Arch Johnston, director of the University of Memphis Center for Earthquake Research and Information, told The Associated Press that instead of helping absorb the wave, the soil in that part of the New Madrid Fault zone "sort of resonated out to longer distances."
The assessment was consistent with recent computer models showing seismic waves would become trapped in the sediment layers, bouncing back and forth between the surface and the hard bedrock thousands of feet below. Researchers said that could amplify high-frequency ground motion, increasing the hazards from large quakes.
But Kiefer said blast waves are at a much higher frequency and much lower amplitude than seismic waves.
"It's kind of comparing apples and oranges," he said, explaining that the Fulton County tests should provide better data. "...Unfortunately, I don't think the kinds of waves that are generated by these blasts would give us the answer."
Woolery said the preliminary information from the Memphis-area blasts "is not overly surprising" and supports the idea that smaller shock waves are amplified and larger waves are muted by the abundance of soil above bedrock.