USGS says Chicago's western suburbs hit by quake

[November 15, 2013]  CHICAGO (AP) — Scientists of the U.S. Geological Survey say it's likely it was an earthquake that shook Chicago's western suburbs after a blast at a quarry.

USGS scientist Jim Dewey says research indicates quarry blasts don't cause larger follow-up tremors. However, a quarry blast in McCook was followed by a related tremor seven seconds later.

Dewey says USGS scientists now believe the blast triggered a release of tectonic strain at a shallow depth, not miles deep in the earth's crust where earthquakes usually originate.

The USGS and Hanson Materials, owner of the quarry, will install a seismograph in the quarry which will make hourly readings of the earth's behavior.

The Nov. 4 tremor shook several communities southwest of Chicago. There were no reports of damage or injuries.

[Associated Press]

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