Shaking felt in the western suburbs on Monday afternoon was being attributed to a quarry blast, officials with the United States Geological Survey said.
The NBC Chicago newsroom began receiving numerous calls of shaking felt in Hinsdale, Willowbrook, Des Plaines and Willowsprings at about 12:40 p.m.
The USGS, citing preliminary information, said a magnitude 3.7 quake shook the area at 12:35:34 p.m. CT. It was about 1.4 kilometers deep, scientists said. They later said the event was related to a quarry blast in Countryside, Ill and downgraded the shaking to a magnitude 3.2 seismic event at 12:35:33. There were no immediate reports of damage or injuries.
The Hanson Material Service quarry in McCook, Ill., issued a statement saying it was performing "routine blasting operation" at about 12:35 p.m. when about seven seconds after the blast "a separate seismic event was recorded."
"We are reviewing the seismic readings in order to get a better understanding of what may have occurred. At this time, we have no reason to believe that there is a connection between our routine blast and this seismic event." the statement read.
McCook Mayor Jeff Topolski is looking for answers.
"That's my extent of concern, is to get to the bottom of this and make sure it doesn't happen again, Topolski said.
Most of the people who live near the quarry, like Vijay Parikh, barely flinch when they hear a blast, but Monday was different.
"This was a huge blast and my house was shaking like crazy," Parikh said.
Ted Steinbrecher was near a forest preserve when he felt and heard it.
"A male deer took off running like he was being chased or someone had shot off a gun," Steinbrecher said.
"My building began to rattle and I felt myself moving back and forth in relation to the noise," Anthony Monks wrote NBC 5 in an email.
Earthquakes in Illinois aren't uncommon. A 2.7 magnitude quake rattled Ewing, Ill., in March and a 3.8 magnitude shook the Chicago area in the early morning hours of Feb. 11, 2010. In April 2008, a 5.2 magnitude earthquake hit West Salem, located 270 miles south of Chicago, becoming the state's worst since 1968.
Earthquakes between 2.5 magnitude and 3.0 are typically some of the smallest felt by humans.