UPDATED 01/31/12 5:45 a.m.
WOODSTOCK, Ill. (CBS) -- Residents of the far northwest suburbs were not dreaming last night – a minor earthquake shook the Illinois-Wisconsin state line.
The quake happened just before 10 p.m. Monday. The epicenter was initially believed to be near Racine, Wis., but Tim Larson of the Illinois State Geological Survey said the epicenter was actually in Illinois just east of McHenry.
While minor earthquakes are common in the Chicago area, they are rare in the northwest suburban region, Larson said.
But it is not yet known why the earthquake struck near McHenry, he said.
"We're still working on that. That's what puts the seismologists through school," Larson said.
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Seismologists say the quake registered with a magnitude of just 2.4. But McHenry County residents felt it.
"Two point four is a very small earthquake; so far, a couple hundred people have reported feeling it. Some people reported a sonic boom or explosion, but it was recorded by at least eight seismometers in the area. That's why we know the magnitude of this earthquake," Larson said.
John Laskowski says the quake hit his house hard and fast, and he was left with no clue as to what had happened.
"My first thought was that maybe there had been a building nearby that had caught fire and blew, or whatever, so I went outside, looked at the horizon, and I didn't see anything; didn't hear any sirens. We just had a lot of neighbors in the area that blow off fireworks, especially in the summertime," he said.
Lt. Donald Carlson of the McHenry County Sheriff's Department says the quake did not cause any damage.
"We have not been contacted in regard to any damage or injuries, and we found none as we patrolled the area trying to find the source," Carlson said.
However, there were calls from Island Lake north all the way to the northern portion of the city of McHenry, Carlson said.
A handful of other earthquakes have shocked the Chicago area in recent years.
On Feb. 11, 2010, a 3.8-magnitude earthquake struck an epicenter 1 mile south-southeast of Pingree Grove, which is about 40 miles northwest of Chicago.
No serious damage was reported, but many people reported thinking they heard an explosion when the earthquake struck.
CBS 2's Mary Kay Kleist was preparing the morning's weather forecasts at the CBS 2 Broadcast Center at the time, when lights started moving in the studio, and, "suddenly, I thought a truck was going to hit the building."
On April 18, 2008, a 5.2 magnitude earthquake struck with an epicenter about 7 miles from downstate Mt. Carmel, about 230 miles south of Chicago. That earthquake was felt around the state, including in Chicago.
Downtown skyscrapers shook, but damage was mostly seen downstate.
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