A predawn earthquake rattled Southern Illinois and eastern Missouri early today, waking up neighborhoods across the area and flooding police departments with calls.

The quake measured a 5.2 magnitude and occurred at 4:37 a.m. CDT. It was centered in southeastern Illinois, five miles from the town of Bellmont, according to Timothy M. Kusky, director of the Center for Environmental Sciences at St. Louis University.

"It was felt rather strongly here in St. Louis," Kusky said. "It woke many people up. It woke me up. It woke my cat up."

People felt it the shaking anywhere from five to 30 seconds.

A 4.5 magnitude aftershock came at 10:14 a.m.

In St. Louis, the only reported damage was of concrete that fell from the 72-year-old South Kingshighway viaduct over the Union Pacific line at Shaw Boulevard. City engineers closed the bridge to inspect it, then reopened some of the six lanes about 6:30 a.m. They reopened all lanes two hours later.

Tom Bean, the city's chief construction engineer, said the earthquake broke away pieces of concrete from several places on the deck and supports where there had been old surface cracks and salt erosion. He said the inspection determined that the bridge's structure was not damaged.

Because of its age, the hump-shaped bridge already has a weight restriction for traffic. Bean said the city is in early planning to replace the bridge within the next few years.

Some reported that windows or foundations had cracked, but police had no immediate reports of major damage.

"We've had a lot of calls from people whose windows rattled, stuff fell off of shelves, but no damage," said Sgt. Michael Gordon of the Alton Police Department.

More than 1,000 Ameren Illinois customers near West Salem briefly lost power after this morning’s earthquake, said spokesman Leigh Morris. The outage started around 4:51 a.m. and customers were back on by 6:31 a.m., he said.

Ameren isn’t aware of any damage to its electric or natural-gas ditribution systems.

"We are patrolling our natural gas transmission lines, but there are no reports of damage or leaks," Morris said.

More than 4,800 Ameren Illinois customers were without power as of 11:45 a.m. Friday, but those outages are related to a traffic accident, not the earthquake. The accident didn’t damage any equipment, but Ameren was asked to cut power to a line a little before 9:30 a.m. to authorities could free a victin trapped in their automobile.

The quake was the result of the moving apart of two tectonic plates along the New Madrid fault, well-known to St. Louis area residents. But instead of being along the main fault line, primarily along the Mississippi River, it originated from a spur known as the Wabash Valley Seismic Zone. The epicenter was in Bellmont, 127 miles east of St. Louis.

The New Madrid Fault is a weak spot in the center of the country caused by the stretching millions of years ago of the earth's surface, the North American Plate, along the fault lines in California and on the mid-Atlantic ridge, Kusky said.

"A 5.2 earthquake is pretty high for here but not very high for around the world," Kusky said. "It takes a little bit more to cause major damage."

Today's earthquake came on the anniversary of the 1906 earthquake that reached 7.8 magnitude and destroyed much of San Francisco.

Since this morning’s earthquake, Missouri Department of Transportation bridge inspectors have been looking at all state bridges in the eastern part of the state that may have been affected by the tremor. So far, no damage has been found.

Before dawn, about 25 MoDOT employees in the St. Louis area began driving the region checking major roads and bridges for problems. It was the first time they’d been able to put the state’s earthquake plan in place under real conditions.

As of 2:30 p.m., MoDOT has inspected 2,000 of the 2,500 bridges that will be examined as a result of this morning's earthquake in Illinois.  No problems have been found.  The remaining 500 bridges to be inspected are in the southeast portion of the state, and those results should be available in the next few hours.

Some of the inspections were done as a drive-by. Others received a closer examination. Some will be re-checked later today for certainty.

"We know some of the most vulnerable points on our major bridges," Blair said. "We have components on our bridges we look for in situations like this for signs of movement."

Bridges built since 1992 are designed to withstand earthquakes much better than those older than 15 years. The department is working to retrofit the Poplar Street Bridge complex so it can survive a major earthquake.

Also today, MoDOT will examine Missouri River crossings at Hermann, Jefferson City, Boonville, Rocheport, Miami and Glasgow.

Inspectors are looking for any signs of damage, including cracks or buckling in the bridge deck, loose pavement, bent beams or girders, missing bolts, or misalignment of curbs or rails. If potential problems are found, bridge engineers will be called in for a more thorough examination, and the bridge will be closed if necessary.  

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No injuries reported

No injuries were reported in Illinois, but at least three families were displaced when an apartment building wall collapsed in Wabash County, in southeastern Illinois near the Indiana border. The Red Cross has been assisting them in finding shelter.
 
Patti Thompson, a spokeswoman for the Illinois Emergency Management Agency, said the agency has received other reports of minor damage to homes in Wabash County and an elementary school in nearby Edwards County. In Lawrence County, also on the Indiana border, there were reports of damaged chimneys, a broken water line and a damaged grain elevator.
 
The Illinois Department of Transportation had crews working at dawn examining roads and bridges in a 50-mile radius from the epicenter of the earthquake. ``They’re looking for deck alignment (problems), cracks, twisting, things like that,’’ said IDOT spokesman Brian Williamsen. There were no immediate indications of problems, he said.
 
IDOT’s aeronautics division is also examining all runways at airports across the state.
 
Illinois Gov. Rod Blagojevich issued a statement early Friday announcing he had mobilized the State Emergency Operations Center, which is designed to coordinate efforts of various state agencies during emergencies.
 
The state is ``in contact with officials throughout southern Illinois to get information about the impact of the earthquake,’’ Blagojevich said in the statement. ``Fortunately at this point, the damage reported appears to be minor.’’

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At the epicenter

Meanwhile, at the quake's epicenter, it wasn't the shaking that woke Vicki Rayborn, who lives in Bellmont. It was turkey season. Rayborn's husband had just left home to go hunting, so she was awake and watching television when the quake struck.
 
"The whole house started shaking and all my whatnots were falling," she said.
 
 Along with the shaking came a mighty roar, she said, much like a thunderstorm or train. Her police scanner even talked about reports of a train derailment. "All the sirens were going off and the scanner talked about a derailment, and then they realized it was really an earthquake," she said.

In West Salem, Ill., a town of 1,100 people about seven miles from the epicenter, police chief Harvey Fenton said he felt his two-story brick home rumble for about 30 seconds.

"I thought it was going to collapse and I'd end up in the basement," Fenton said. "It was an exciting wake up call. I hear this big bolt, and my impression for the first second was, it was a thunder bolt or an explosion."

Fenton said the worst damage were small cracks to the foundation of the West Salem Grade School. It wasn't a big deal, though, he said, and school was going on as planned today.

In Mount Carmel, 15 miles southeast of the epicenter, one woman was briefly trapped in her home by a collapsed porch but she was quickly freed without injury, said Mickie Smith, a dispatcher at the police department.

In Carmi, Ill., about 35 miles south of the epicenter, city clerk Don Kittinger said he was awake "when I started to hear the sound. I thought it was a freak tornado or some major storm. It got louder before we actually felt the shake. There was a whole lot of shaking going on, but nothing fell, no pictures or anything."

Kittinger said the only report of damage was of bricks that fell from the chimney of an old, unoccupied home that is scheduled for demolition. Mount Vernon, 50 miles west of the epicenter, had no reports of damage, according to the building inspector's office.
 
In Philo, a town about 10 miles south of Champaign, David Behm said the quake woke him up.

"For people in central Illinois, this is a big deal. It's not like California," he said.

Most people calling police reported windows rattling and beds shaking. People as far north as Chicago and as far east as Cincinnati reported feeling the quake, which apparently caused some minor damage in the Louisville, Ky., area. Video of some buildings in Louisville showed fallen bricks. One report even said it was felt in as many as seven states, including Wisconsin and Ohio.

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What to expect now

Kusky said aftershocks typically decrease in intensity and could come a day or two later.

He said a 5.2 in the Midwest is felt more than if the same quake were to happen in California because of rock and soil conditions here.

"In the midwest, the rocks tend to be harder so we can feel it more," he said. "It shakes the ground longer. In California, the rocks are more soft and it dissipates more quickly."

If some people felt the earthquake lasted only a few seconds -- while others felt it lasted 20 or 30 seconds -- Kusky said it's based on the foundation of people's houses. A house whose foundation sits on solid bedrock, he said, probably only felt about 5 seconds of shaking. If a house is on a more porous foundation of clay, people probably felt shaking for about 20 seconds.

J. David Rogers, professor of geological engineering at Missouri University of Science and Technology, said the Wabash Valley Seismic Zone is "definitely capable of spawning 7.0 magnitude earthquakes approximately every 1,000 years. We know there was a large event about 4,600 years ago -- a magnitude 7 or above."
 
There also were large ones in 1891, 1968 and 1987.
 
"This zone has been crackin' off magnitude 5-plus events, and quite a few historic ones," Rogers said. The Missouri University of Science and Technology is based in Rolla.
 
One problem is that the federal or state governments haven't pumped money into research in the Wabash Valley zone like they have for the New Madrid quake zone.
 
 The 1968 quake, with its epicenter near Dale, Ill., was about 35 miles from the Wabash River. It measured a 5.3 magnitude. In June 1987, a 5.0 magnitude quake was centered in Olney, Ill., just north of today's earthquake.
 
Rogers said a 5.2 quake, which today's was, might cause shaking for 10 seconds and shouldn't cause a whole lot of damage.

"It might knock down a few chimneys, but we don't expect it to cause gross structural damage," Rogers said.

Across many otherwise dark neighborhoods, lights went on as people climbed out of bed to check for damage. Dozens of houses in a Freeburg neighborhood lit up before the shaking stopped, and emergency phone numbers began ringing almost immediately, police said.

"Everyone's been calling," said a woman answering phones for the Freeburg police.

J. W. True, a security guard at The Lofts at Lafayette Square in St. Louis, was patrolling near an abandoned factory next to the apartments when he heard a sound in the metal vents above him.

"It rattled them real good," True said. "I was nine hours into my shift, and that really woke me up. I thought, 'Did I really feel that?'"

He started walking back to the apartments and one of the tenants shouted down from a 4th floor window and yelled, "Is that what I thought it was?"

Kusky said the quake originally had been recorded at 5.4 on the Richter scale by the U.S. Geological Survey, but it was downgraded to 5.2 by about 6 a.m. The force produced by a 5.4 are less than 10 times greater than a 5.2

Kusky said it's not unusual for the number to be revised.

"It's a complicated calculation and we have to take measurements from different seismic stations all around," he said. "It takes a little bit of time to average all the stations."

The earthquake should be a reminder to St. Louis residents, Kusky said, that we do live in an earthquake-prone area. He suggested that residents consider getting earthquake insurance. He recommends they not sleep with any large objects on the wall above them and keep life-sustaining supplies on hand. But not to worry, the huge earthquakes like the devastating series of quakes in 1811 and 1812 come just once every 400 or 500 years.

"We do live in an area that has earthquakes every once in a while," Kusky said. "We can have larger earthquake events and we should be prepared."

In the Fort Zumwalt School District in St. Charles County, West Middle School went into earthquake mode after teachers and students on the upper floors of the building felt a mid-morning aftershock.
 
"Computers were shaking and they could feel swaying," Principal Lori Jessen said. "It was nothing horrible, but they could feel it."
 
Amanda St. Amand, Kim Bell , Carolyn Tuft , Steve Giegerich and Jessica Bock of the Post-Dispatch contributed to this report, as did the Associated Press.