Philadelphia, Pennsylvania – A rare Midwest earthquake early Tuesday is now drawing attention in Pennsylvania as Arctic air surges east, sending temperatures sharply lower and creating conditions that could lead to frost quakes during the coldest overnight hours.
According to the U.S. Geological Survey, a 3.5 magnitude earthquake struck central Illinois shortly before 2 a.m. Tuesday, centered about 35 miles south of Springfield. The shallow quake was felt across a large portion of Illinois, with thousands reporting shaking and loud rumbles before sunrise. While no damage was reported, earthquakes of that magnitude are uncommon in the Midwest, making the event notable as extreme cold settles in.
As the deep freeze reaches Pennsylvania, geologists say rapid temperature drops can trigger frost quakes, also known as cryoseisms. These occur when moisture in the ground freezes quickly, causing soil and rock to contract and crack suddenly. The resulting boom or vibration can feel like a small earthquake and may rattle homes, especially late at night or before dawn.
Parts of central and northern Pennsylvania, including Harrisburg, State College, Scranton, and areas of western Pennsylvania, may be more susceptible as temperatures fall into extreme cold following recent precipitation. Frost quakes are shallow and localized but can crack pavement, foundations, and underground utilities.
Emergency officials stress that frost quakes are typically harmless, but residents should remain alert, inspect property if shaking is felt, and report loud booms or ground movement to local authorities or the USGS. With dangerous cold expected to persist through midweek, additional advisories or alerts may follow as conditions evolve.
