The following facts pertain to earthquakes that have hit Illinois.
Largest earthquake in Illinois (until April 18, 2008)
Location: Southern Illinois
Occurred on: Nov. 9, 1968
This was the strongest felt earthquake in southern Illinois since the 1895 Missouri event. Property damage in the area consisted mainly of fallen bricks from chimneys, broken windows, toppled television aerials, and cracked or fallen plaster. In the epicentral area, near Dale, Hamilton County, MM intensity VII was characterized by downed chimneys, cracked foundations, overturned tombstones, and scattered instances of collapsed parapets.
Most buildings that sustained damage to chimneys were 30 to 50 years old. A large two-story brick house near Dale, Illinois, sustained several thousand dollars damage. About 10 kilometers west of Dale, near Tuckers Corners, a concrete and brick cistern collapsed. A large amount of masonry damage occurred at the City Building at Henderson, Kentucky, 80 kilometers east-southeast of the epicenter. Moderate damage to chimneys and walls occurred in several towns in south-central Illinois, southwest Indiana, and northwest Kentucky. Felt over all or parts of 23 States: from southeast Minnesota to central Alabama and Georgia and from western North Carolina to central Kansas. People in multistory buildings in Boston, Massachusetts and southern Ontario, Canada, felt the earthquake.
(Source: USGS, http://earthquake.usgs.gov/regional/states/events/1968_11_09.php)
Illinois Earthquake History (Major events)
May 25,1909: Aurora, Illinois - M 5.1
November 9, 1968: Southern Illinois - M 5.3
June 10, 1987: Near Olney, Illinois - M 5.1
June 28, 2004: Illinois - M 4.2
January 2, 2006: Illinois - M 3.6
(Source: USGS, http://earthquake.usgs.gov/regional/states/index.php?regionID=13)
DAMAGING EARTHQUAKES IN ILLINOIS
Earthquakes occur in Illinois about once every year. But damaging quakes are much less frequent.
Minor damage from Illinois earthquakes is reported about once every 20 years.
Serious damage from earthquakes occurs every 70 to 90 years.
Devastating earthquakes are very rare in the central US, occurring about once every 700 to 1200 years.
The last strong earthquake to strike the Midwest happened on Halloween (Oct. 31) 1895.
The quake, centered just south of Illinois in Charleston, Missouri, had an estimated magnitude of 6.8 on the Richter scale.
It was felt as far away as Pittsburgh, Pennsylvania, New Orleans, Louisiana, and Topeka, Kansas.
(Source: EARTHQUAKE FACTS - Illinois State Geological Survey 1995-2 Department of Natural Resources)