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Cause Of Tremors In Suburbs Likely A Quarry Blast

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Northwestern University seismic station at Ryerson Woods Conservation Area in Lake County, IL. measured Monday's tremor.

Northwestern University seismic station at Ryerson Woods Conservation Area in Lake County, IL. measured Monday’s tremor.

UPDATED: 11/4/2013 4:10 p.m.

INDIAN HEAD PARK, Ill. (CBS) – Residents in the western suburbs felt tremors early Monday afternoon, and federal officials believe the shaking was from a quarry blast and not a natural earthquake.

The Hanson Material Service quarry acknowledged it was performing routine blasting operations in McCook, not far from the epicenter of the event.

However, spokesman Jeff Seig said “we have no reason to believe that there is a connection between our routine blast and this seismic event.”

About seven seconds after a blast around 12:35 p.m. a “separate seismic event was recorded,” Seig said.

He said the company was reviewing the data to better understand what may have occurred, adding the seismic readings were below regulatory limits.

The U.S. Geological Survey originally said a 3.7 magnitude earthquake was recorded at 12:35 p.m. in Indian Head Park. Later, the USGS downgraded the tremor to a 3.2 magnitude tremblor from a quarry blast in Countryside.

Representatives at Vulcan Materials quarry in McCook, along the border with Countryside, said they were not blasting on Monday.

Mary De Groot of LaGrange was walking home from her children’s school when she felt the earth move.

“This was more like an explosion,” she said. “I saw my house come off the ground and I was lifted off the ground.”

Inside her home, pictures were knocked askew by the force of the shock.

Across the street, at a house being prepared for an estate sale, even more dramatic effects. A water pipe burst moments after the shock was felt.

A representative for the USGS told WBBM Newsradio a 3.7 magnitude tremor (later revised to 3.2) is somewhat large for a quarry blast, so they were still investigating.

Several local residents tweeted about feeling the ground shake.

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