The earth rattled in the Chicago area Monday afternoon, but it turned out the fault (so to speak) was with man and not nature.
WGN-TV reports that a "shot" blast at Hanson Materials in suburban Hodgkins, Ill.,
was to blame for what the U.S. Geological Survey recorded as a
magnitude-3.2 earthquake at 12:35 p.m. CST Monday. Initially, the USGS
had rated the magnitude as 3.7.
The USGS website received reports
of shaking across many of Chicago's western and southwestern suburbs, as
well as parts of the city itself, generally within a 15-mile radius of
the quarry blast. Most of these reports were characterized as weak or
light. A few spotty reports of shaking came in from the northwestern
suburbs as well. No serious damage was reported.
Two major
quarries operate in the vicinity of the reported epicenter. According to
Google Maps, less than a mile separates the Hanson Materials site from
the larger McCook Quarry, both located about 15 miles west-southwest of
downtown Chicago.
Jeff
May, senior area operations manager for Vulcan Materials Company, which
operates the McCook Quarry, confirmed his company did not conduct any
blasting activity Monday.
(WATCH: Chicago Forecast)
Joshua
Robbins, spokesman for Vulcan, said that quarries typically keep close
tabs on the impact of their blasts, which in the industry are called
"shots."
"The shots are all measured. There are seismographs.
Quarries typically measure it at multiple locations," Robbins said.
"Each shot is recorded ... usually at multiple points."
He
explained that quarry shots are typically done by drilling holes into
the limestone rock and using ammonium nitrate fuel oil mixture to do the
blasting. He noted that most states have a Department of Natural
Resources that regulates such activity.
Robbins said it would be
hard to imagine a quarry blast being large enough to cause structural
damage. "In my company, we send out structural engineers to evaluate
claims of blast damage."
http://www.weather.com/news/quarry-blast-earthquake-20131104
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