Recent studies have indicated that the New Madrid Seismic Zone is not
the only 'hot spot' for earthquakes in the Central United States. On
June 18, 2002, a 5.0 magnitude earthquake struck Evansville, Indiana
with an epicenter between Mt. Vernon and West Franklin in Posey County,
in an area that is part of the Wabash Valley Seismic Zone. According
to the Indiana University Indiana Geological Survey, while there was
minor damage associated with the earthquake, the tremor was a warning
to residents of the Wabash Valley Seismic Zone that earthquakes can,
and do, strike close to home.
to the USGS , this map of the New Madrid and Wabash Valley
seismic zones shows earthquakes as circles. Red circles
indicate earthquakes that occurred from 1974 to 2002
with magnitudes larger than 2.5 located using modern
instruments. Green circles denote
earthquakes that occurred prior to 1974. Larger earthquakes are represented by larger
circles. Map Source USGS FS-131-02
On April 18, 2008, a 5.4 magnitude earthquake struck near Mt. Carmel, Illinois, further demonstrating that earthquakes are topic that needs to be addressed. This earthquake was felt in at least 16 states, by more than 40,000 people, according to the USGS. Fortunately, there were no serious injuries or fatalities, but non-structural damage was reported in the states of Illinois, Indiana, & Kentucky.
The Wabash Valley Seismic Zone is located in Southeastern Illinois and Southwestern Indiana and it is capable of producing 'New Madrid' size earthquake events. Since the discovery of this seismic zone, earthquake awareness and preparedness have increased. Residents are seeing that moderate sized earthquakes are not just occurring to the south, but occur right at home and can affect Illinois, Indiana, and Kentucky.
Geologists in Indiana and Illinois have found liquefaction sites and sand dikes that shows the evidence of prehistoric earthquakes in the region. By examining the size of the dikes and sediment found within the sand dikes, geologists are able to estimate the size of the earthquake it took to create the formations. In the mid-1980’s, geologist Steven Obermeier found a liquefaction formation that was estimated, through carbon dating, to be 6,100 years old. The earthquake that produced the site was estimated to be a magnitude 7.1, large enough to seriously disrupt the area known as the Wabash Valley Seismic Zone.
Current research is still turning out new evidence of historic earthquakes in the zone. For further information on the Wabash Valley Seismic Zone, browse through the links below.