With the exception of the New Madrid area, we don’t get as many earthquakes in the mid-west, but the few we do get are of a different breed than most costal area quakes. The rock structure in the mid-west and east is more rigid and therefore it transfers the shocks over longer distances. The great New Madrid quake of 1812, was probably about 8.0 on the scale, and the shaking was felt strongly over 50,000 square miles and moderately over a million square miles. By contrast the great San Francisco quake of 1906 was of about the same magnitude, but the limits of its moderate impact were only 6,000 square miles. The 1812 quake in New Madrid, Missouri reputedly caused church bells to ring in Boston. That would be like a San Andreas quake shaking up Denver.
A big area of Southern Missouri, Illinois, Indiana, Western Kentucky, Tennessee and NE Arkansas are fractured with fault lines, sometimes directly from the New Madrid hotspot, but often independent.
As a result, the moderate quake this morning was felt in many states: Michigan, Wisconsin, Iowa, Missouri, Kansas, Arkansas, possibly Oklahoma, Mississippi, Alabama, Georgia, Tennessee, Kentucky, possibly Virginia, West Virginia, Ohio, Indiana, and Illinois; maybe more.