DeKalb – A mild earthquake shook northern Illinois this morning.
The U.S. Geological Survey reported a 4.3-magnitude quake about 3:59:43 a.m. centered about 5.5 miles east of Sycamore and 3.1 miles underground. The epicenter is about 45 miles west of Chicago.
The quake was felt over a wide area, but there were no immediate reports of any damage.
At this point the fault activity that caused the quake was unclear, said Amy Vaughan, a geophysicist with the geological survey in Golden, Colo. Past quakes that have affected southern Illinois have been caused by the Wabash Valley or New Madrid seismic zones.
The fault systems in northern Illinois are not as well understood as those in other regions where earthquakes are more common, and more investigation will be needed to determine the cause of this morning's temblor, Vaughan said.