Was it thunder? Was it wind? Was it a passing truck or train? Was it the refinery?
When sleepy Crawford Countians finally woke up around 4:30 a.m. today, they realized the seismically active region had come to life again.
A 5.2-magnitude earthquake centered in southern Illinois rattled homes and skyscrapers across the Midwest, causing little damage but surprising residents unaccustomed to such a powerful temblor.
The quake - one of the strongest ever recorded in Illinois - occurred just before 4:37 a.m. and was centered six miles southeast of West Salem and 66 miles west of Evansville, Ind.
Initially pegged as a 5.4 earthquake, the U.S. Geological Survey revised its estimate to give it a value of 5.2.
A major aftershock was felt about 10:15 a.m. It was magnitude 4.5, and also centered near West Salem.
No damage has been reported in Crawford County to this point. Crawford County Superintendent of Highways Justin Childress told the Daily News today all roads in the county are fine, and highway department personnel are in the process of assessing damage, if any, to the county's bridges.
"Bridges are more affected by something like this," Childress said. "We will start with the lowest-rated structures first and then look at the bigger structures."
Robinson Wastewater Treatment Facility Superintendent Lawrence Quick said no damage could be found at the plant, adding the plant is designed to move the predicted amount for seismic activity in this area. The Robinson-Palestine Water Commission also reported everything is operating normally with its equipment and structures. Operations were also normal at the Ameren Energy Generating Station in Hutsonville, according to spokesperson Debbie Goodwin.
The Marathon refinery had not responded to a Daily News call by presstime, but no emergency siren was sounded following the quake.
Citizens throughout the county experienced the quake in different ways. Robinson Police Sergeant Rob Hargrave said it shook some of the mortar loose from the brick walls of his residence on North Jefferson. He did not believe there was any structural damage to his home occurred.
City of Robinson Administrative Assistant Laquita Hasty said the dishes in her china cabinet rattled, while Crawford County Jail Administrator Henry VanWinkle said when he first heard the tremor, it sounded like a car had driven into his house.
In addition to the Richter scale measurement, the USGS calculates a quake's intensity based on citizen reports on a 12-level scale, which refers to the effects actually experienced at a particular place.
The intensity in Lawrenceville averaged 5 on the scale, from 24 reports as of 11 a.m. In Crawford County, the intensity in Robinson was at level 4 based on 29 reports; Palestine, level 5 with four reports; Oblong, level 4 based on three reports; and Hutsonville, level 3 based on six reports.
In Mount Carmel, 15 miles southeast of the epicenter, a woman was trapped in her home by a collapsed porch but was quickly freed and wasn't hurt, said Mickie Smith, a dispatcher at the police department. The department took numerous other calls, though none reported anything more serious than objects knocked off walls and out of shelves, she said.
As the sun rose and residents began checking their homes and businesses, isolated incidents of bricks lying on the ground and cracked chimneys were reported, according to the Mt. Carmel Daily Republican-Register. The ground shook enough to send bottles crashing to the floor inside Wagon Wheel Discount Liquor in Mt. Carmel.
Fallen bricks literally left behind holes in the old Berry School on West Sixth Street in Mt. Carmel, a property that had been converted into apartment housing. Residents were reportedly inside the building at the time, and were evacuated pending investigation of the structure. No injuries were reported.
In West Salem, dispatcher Lucas Griswold said the sheriff's department received several calls about the earthquake, but only reports of minor damage and no injuries.
"Oh, yeah, I felt it. It was interesting," Griswold said. "A lot of shaking."
Dallas Krumm of Lancaster said he was reading at 4:30 a.m. when he heard the rumbling noise of the approaching earthquake and a thunder-like sound in a distance. "The shaking lasted 22 seconds," he observed.
Krumm said his neighbors reported hearing a "real loud crashing boom like a tornado, followed by two or three additional loud storm sounds."
He said pictures fell off the walls of the mobile home he lives in at Lancaster, and the quake gave a "sensation of floating" as he tried to walk around.
Krumm noted aftershocks occurred at 5:32 and 5:54 a.m.
The quake shook skyscrapers in Chicago's Loop, 230 miles north of the epicenter, and in downtown Indianapolis, about 160 miles northeast of the epicenter.
U.S. Geological Survey scientists in Denver were examining data about the quake, said geophysicist Carrieann Bedwell.
"This was widely felt, all the way to Atlanta, a little bit in Michigan," she said.
Residents in Milwaukee, Cincinnati, Louisville and St. Louis also reported feeling the earth shake. In Louisville, the quake caused bricks to fall off part of a building near downtown, and television video showed bricks strewn in the street, but the mayor's office said there were no reports of injuries.
"It shook our house where it woke me up," said David Behm of Philo, 10 miles south of Champaign. "Windows were rattling, and you could hear it. The house was shaking inches. For people in central Illinois, this is a big deal. It's not like California."
Phones started ringing at the Crawford County Sheriff's Department, but there were no immediate reports of damage, dispatcher Marsha Cravens said.
"They didn't know if it was the refinery blowing up or an earthquake," she said.
In Cincinnati, one woman said she felt something that lasted for up to 20 seconds.
"All of a sudden, I was awakened by this rumbling shaking," said Irvetta McMurtry, 43. "My bed is an older wood frame bed, so the bed started to creak and shake, and it was almost like somebody was taking my mattress and moving it back and forth."
The strongest earthquake recorded in Illinois was in 1968, a 5.3-magnitude temblor centered near Dale in Hamilton County, about 75 miles southeast of St. Louis, according the USGS. Minor damage was widespread, but there were no serious injuries or fatalities.
The Midwest, most notably southeast Missouri and southwest Illinois, is home to the New Madrid fault, a network of deep cracks in the earth's surface.
This quake, according to the earthquake center at St. Louis University, was the result of the moving apart of two tectonic plates along the New Madrid fault, at the center of the country's most active seismic zone east of the Rockies. 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 New Madrid fault, at the center of the country's most active seismic zone east of the Rockies, produces numerous small quakes a year, most too weak to be noticed by the public. But in 1811 and 1812, it produced a series of earthquakes estimated at magnitude 7.0 or greater.
Crawford County is actually part of the Illinois Basin-Ozark Dome region, according to the USGS, which borders the New Madrid zone on its north and west. The region covers parts of Indiana, Kentucky, Illinois, Missouri, and Arkansas and stretches from Indianapolis and St. Louis to Memphis.
The Wabash Valley Fault in southeastern Illinois, southwestern Indiana, and adjacent corner of Kentucky extends about 60 miles north-northeast from the Shawneetown area.
Moderately frequent earthquakes occur at irregular intervals throughout the region, according to USGS. Moderately damaging earthquakes strike somewhere in the region each decade or two, and smaller earthquakes are felt about once or twice a year. In addition, geologists have found evidence of eight or more prehistoric earthquakes over the last 25,000 years that were much larger than any observed historically in the region.
Even before Friday, earthquakes - or the possibility of them - in the central U.S. were getting plenty of attention.
Early next month, agriculture extension officials from various regional states a lready are scheduled to convene an earthquake summit, hosted by the University of Illinois' extension service.
Planners of the New Madrid Earthquake Emergency Preparedness Conference in the Ohio River community of Metropolis, Ill. say representatives from Illinois, Arkansas, Indiana, Missouri and Tennessee are to attend.