But as shown by Friday morning's 5.2-magnitude temblor, centered in this southern Illinois town, the ground beneath America's heartland has a wild side. And though it may not be as likely or imminent as on the West Coast, some experts believe the Midwest needs to speed preparations for its own "big one."
"Mother Nature sent us a wake-up call," said Andrew Velasquez III, director of the Illinois Emergency Management Agency.
Officials say in some realms, such as bridge construction and disaster planning, the region has been making progress. But action has been spotty in other areas, especially building codes.
In recent years, small Midwest earthquakes have been more frequent. Scientists are scurrying to learn more about a region generally known as the New Madrid Zone, where four to six major faults crisscross the Mississippi River basin near the confluence of the Ohio and Mississippi Rivers.
To better understand that, geologists have embedded seismometers in the ground to detect sign of shifts in the earth's crust. Global positioning systems are in place to gauge minute movements. Radar is used to detail topographical and underground changes after quakes.
And scientists are mapping changes in the landscape over thousands of years, hoping to find a pattern behind the earthquakes.
"It's an extremely complex system," said John Holbrook, a professor of earth and environmental science at the University of Texas-Arlington studying the earthquake habits of the New Madrid region. "We haven't quite figured it out."
With conflicting data and interpretation, what it all means is being debated. While disagreeing over the significance of recent ground movement, geologists caution against alarm. In an area more prone to flooding and tornadoes, a major earthquake remains a far less likely possibility, geologists say.
And Friday's earthquake and its aftershocks offer no clues as to whether the region is any closer to a big earthquake, they say.
Seth Stein, a Northwestern University professor of geological sciences, said his global positioning system data indicates fault movement in the New Madrid region is tiny, suggesting to him that the system's pent-up power decreased greatly after the big 19th century earthquakes.
"There is some earthquake hazard in the Midwest, but almost all of that problem is in California," Stein said, noting that earthquakes are less likely to kill an average person than roller skating or football injuries. "I don't know that I'd put this high on the list of public concerns."
Still, authorities across a five-state region were again warning residents to be prepared.
A severe earthquake -- even a moderate quake, centered closer to Memphis or St. Louis -- would have severe impacts.
Despite increased awareness of the risk, building codes safeguarding against the effects of earthquakes in the Midwest are inconsistent. Missouri and Illinois have no state standards, leaving it up to counties and communities to decide.
For the most part, only modern high-rises and public buildings in the Midwest have been constructed using a 1990s building-industry standard designed to resist a big quake.
Heavy brick buildings with decorative masonry are vulnerable to quakes. That is an architecture widespread in both Memphis and St. Louis, the largest cities close to the quake zone, ones that could suffer much damage and many lost lives.
But states are actively retrofitting bridges across the region to protect against seismic shock.
And most states have upgraded emergency response plans, holding more drills and fine tuning details of reactions to earthquakes of varying magnitudes.
Tennessee will hold a state-level earthquake preparedness drill for the National Guard in the coming days, state officials said. Missouri will hold a state workshop next month.
Illinois is urging residents to prepare for earthquakes as they would tornadoes or ice storms, by storing supplies, water and flashlights.
"It's not a matter of scaring people, but in my job, it's a matter of placing the issue out there: This is a hazard," said Steve Besemer, the earthquake program manager for the Missouri Emergency Management Agency. "It is definitely more of a `when' issue than something of an `if' issue for whether there is an earthquake here."
But even as they were shaken awake Friday morning, residents of West Salem near the Indiana border say they worry more about calamities such as floods and tornadoes than about earthquakes. Until the ground started shaking early Friday, the main topic of conversation in this small rural town was the unusually wet spring.
"It was, `Hey, how much is in your rain gauge today?' Now, it's about the quake. `Did you have anything break? Did you see we were mentioned on CNN?'" said Larry Shein, owner of the West Salem Village Cafe. "It scared a lot of people, but I'm getting a kick out of it."
Mayor Eric Goldsmith said four or five years ago there was a large effort to make sure people were prepared if an earthquake hit. The county passed out pamphlets about what to do in an earthquake and about making a survival kit, which he said many in his community did.
But in the last few years, talk of the "big one" seemed to die down. It seemed there weren't as many tremors, at least that residents could detect, so public awareness died down.
"This one kind of caught us off guard," he said of Friday's quake. "It seemed there used to be a lot more people with stockpiles of water or batteries in case we had a real serious one that knocked out the power. It's something that we need to go back and revisit to make sure everyone is prepared again."
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(Chicago Tribune reporters James Janega, Jeremy Manier and Jeffrey Meitrodt contributed to this report.)
(c) 2008, Chicago Tribune. Distributed by McClatchy-Tribune Information Services via Newscom
