How likely is an earthquake in the Midwest, South? The Big One could be coming(Source usatoday.com)

The question is not if a massive earthquake will hit more than a half dozen states that border the Mississippi River, but rather when it will happen.

A minor earthquake early Wednesday that centered on Decatur in East Tennessee about 60 miles southwest of Knoxville was felt into Georgia, Kentucky, North Carolina and South Carolina.

“A 4.4 magnitude earthquake is a reminder for people to be prepared,” said John Bobel, a public information officer for the division of emergency management in Kentucky’s Lexington-Fayette Urban County Government. People see indoor objects shake with magnitude 4 to 4.9 quakes, but the quakes generally cause little to minimal damage.

Scientists have seen evidence that the central Mississippi River Valley has seen major earthquakes for more than 4,000 years.

Today the zone threatens Alabama, Arkansas, Illinois, Indiana, Kentucky, Mississippi, Missouri and Tennessee. That’s a different set of faults than Wednesday’s quake in the East Tennessee Seismic Zone.

Back in 1811, New Madrid, Missouri, itself had only 400 people, St. Louis to the north had about 1,500 residents and Memphis to the south wasn’t even a twinkle in its founders’ eyes, according to the Central United States Earthquake Consortium. Damage was reported as far away as Charleston, South Carolina, and the District of Columbia; and the quakes, estimated at 7.5 to 7.7 magnitude, were felt more than 1,000 miles away in Connecticut.