Around lunchtime today, residents in Chicago's western suburbs felt the earth shake. As WLS-TV reported, they assumed it was an earthquake and the United States Geological Survey reported it as a 3.7 magnitude quake.
While rare, earthquakes do happen in this part of the country. This would have been a significant one for the area.
Interestingly, after the USGS looked at their data, they came to the conclusion that the tremor was actually caused by a quarry blast.
The Chicago Tribune explains:
"The blasting was strong enough to register 3.7 on seismographs. But the U.S. Geological Survey said the wave patterns do not match those from a quake.
"'Based on what they've looked at, we're pretty sure it's from a blast,' said Paul Caruso, a geophysicist with the Survey. 'It is not an earthquake.' ...
"Anything above a 2.5 magnitude can be felt, he said, and a 5.5 magnitude can cause damage.
"A Hinsdale police officer said the department had been notified that there was blasting at the quarry today. They immediately got reports from concerned residents. 'They felt it for quite aways,' the officer said.
"A Westchester resident said 'the entire house shook for one or two seconds, knocking some things off shelves.'"