Chicago, Illinois – A rare Midwest earthquake early Tuesday, Jan. 20, is now heightening concern across Wisconsin and Illinois as a powerful surge of Arctic air sends temperatures sharply lower, creating conditions that could trigger frost quakes across the region.
According to the U.S. Geological Survey, a 3.5 magnitude earthquake struck central Illinois shortly before 2 a.m. Tuesday, Jan. 20, centered about 35 miles south of Springfield near Ohlman. The shallow quake was felt across much of central Illinois, with thousands reporting shaking, rumbling, and rattling windows before sunrise. No injuries or damage were reported, but earthquakes of this size are uncommon in the Midwest, making the event notable as extreme cold quickly followed.
Geologists say the timing is significant because rapid temperature drops associated with this Arctic outbreak can trigger frost quakes, also known as cryoseisms. These occur when moisture in the ground freezes suddenly, causing soil and rock to contract and fracture. The result can be a loud boom or brief shaking that may feel similar to a small earthquake, often happening overnight or before dawn.
Parts of southern and central Wisconsin and northern Illinois, including Milwaukee, Madison, Rockford, Chicago, Kenosha, Racine, and communities along the I-90 and I-94 corridors, may be more susceptible as temperatures plunge following recent snow or wet ground conditions. Frost quakes are shallow and localized but can crack pavement, foundations, and underground utilities.
Emergency officials emphasize that frost quakes are not tied to fault lines and do not signal larger earthquakes. Residents are encouraged to remain alert during the coldest hours, inspect property if shaking or loud booms are noticed, and report ground movement to local authorities or the USGS. With dangerous cold expected to persist through midweek, additional advisories or alerts may follow.
