The Earth Shook, but Geologists Don't Know Why
Chicago – Geologists say they cannot give a reason for Monday morning's earthquake centered in the small community of Troy Grove in north central Illinois.
Authorities say the magnitude 4.5 quake caused no reported damage.
The quake, which occurred at 1:10 a.m., was also felt in parts of Missouri, including St. Louis, as well as Indiana, Iowa, Wisconsin and Michigan.
John Bellini of the U.S. Geological Survey's National Earthquake Information Center says at the most it may have caused a picture to fall from a wall or a tall vase to topple from a table.
Northwestern geological science professor Seth Stein says scientists don't fully understand why earthquakes occur in what is thought of as the stable interior of the continent.
He says the continent contains old faults that moved millions of years ago.