Southern Wisconsin may have felt a rare earthquake in north central Illinois

USGS received 2 reports from Wisconsin residents who felt the 3.6 magnitude earthquake early Wednesday morning

A black star, representing the earthquake's epicenter, is surrounded by green and blue representing the quake's intensity
A map from the U.S. Geological Survey shows where the 3.6 magnitude earthquake could be felt. Photo courtesy of USGS

Residents of southern Wisconsin may have felt a tremble early Wednesday morning thanks to a rare earthquake in northern Illinois.

The U.S. Geological Survey recorded a 3.6 magnitude earthquake in Putnam County, Illinois, around 100 miles from the Wisconsin border. The quake happened at 4:41 a.m. and USGS estimates the event could be felt as far as southern Wisconsin, northeast Iowa and northwest Indiana.

The USGS website shows that out of the 413 reports from residents who felt the quake, one came from Milwaukee and one came from Mosinee.

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Three colored lines show the waveform representing the earthqauke
The UW-Milwaukee’s seismometer recorded the 3.6 magnitude earthquake in north central Illinois on Wednesday, November 15, 2023. Courtesy of Brett Ketter/UW-Milwaukee

Brett Ketter is a seismologist at the University of Wisconsin-Milwaukee’s Department of Geosciences. He recorded the quake on the university’s seismometer, an instrument for recording earthquakes.

Ketter said it’s rare for the Midwest to see an earthquake, estimating he’s only recorded five events over his two decades at UW-Milwaukee.

“The thing about these types of earthquakes, especially anything east of the Rockies and in the Midwest area, is even a small earthquake like this is felt over a very wide area because of the underlying geology,” he said.

He said Wednesday’s quake was smaller than previous events, so many Wisconsin residents likely slept right through it. Ketter said someone would need to be awake and in a quiet area to notice the shaking.

“If you’re anywhere near any kind of heavy traffic situation, you’re not going to feel it probably,” he said. “The traffic is going to generate almost more vibration than the earthquake.”

The Chicago Sun-Times reported residents near the quake felt their homes shake and local police saw a flurry of 911 calls.