These earthquakes occurred in the Wabash Valley Seismic zone. The earthquakes in this zone are scattered over a large area of southeastern Illinois and southwest Indiana. The zone had at least eight prehistoric earthquakes over the past 20,000 years with estimated magnitudes ranging from about 6.5 to 7.5, based on geologic evidence. Earthquakes of the size of the recent quake (Mw 5.2) can produce smaller aftershocks over the following days. A few might be large enough to be felt. Typically, earthquakes of this size (Mw 5.2) can cause light damage within a few tens of miles from the epicenter. Central and eastern US earthquakes generally shake areas about 10 times as large as those that occur in California. It is not surprising that this earthquake was felt as far south as Florida.

The Wabash Valley Seismic zone is adjacent to the more seismically active New Madrid seismic zone on the seismic zone’s north and west. The recent earthquake is also within the Illinois basin – Ozark dome region that covers parts of Indiana, Kentucky, Illinois, Missouri, and Arkansas and stretches from Indianapolis and St. Louis to Memphis. Moderately frequent earthquakes occur at irregular intervals throughout the region. The largest historical earthquake in the Illinois Basin region (magnitude 5.4) damaged southern Illinois in 1968. Moderately damaging earthquakes strike somewhere in the region each decade or two, and smaller earthquakes are felt about once or twice a year.

Earthquakes in the central and eastern U.S., although less frequent than in the western U.S., are typically felt over a much broader region. East of the Rockies, an earthquake can be felt over an area as much as ten times larger than a similar magnitude earthquake on the west coast.