Excerpt from the Register-Mail:
Friday morning’s earthquakes were a once-in-a-lifetime event for most people.
According to Mihai Lefticariu, visiting assistant professor of environmental studies at Knox College, while earthquakes of the magnitude felt here in Galesburg are rare in the Midwest, they are not altogether impossible. A magnitude 5.2 quake with an epicenter near West Salem, Ill., shook people awake from Kentucky to Wisconsin around 4:30 a.m.
Earthquakes of a magnitude six — on the 12-point moment magnitude scale, successor to the Richter scale — happen once every 80 years or so, he explained.
This particular quake, aftershocks of which were felt around 10:15 a.m. Friday, originated in the Wabash Fault in the Wabash Valley Fault System, located in southeastern Illinois, southwestern Indiana and a small corner of Kentucky. It is located very near the New Madrid Fault System, a “major fault system that started forming between 700 (million) and 600 million years ago,” Lefticariu said.