Ask A Scientist General Science Archive

Author:     Arlene Langley
Text:       I have read that a strong earthquake occurred in Illinois which 
changed the course of the Mississippi River many years ago.  I was wondering 
what were the most recent earthquakes in Illinois and where they occurred.  
Were they strong enough to do damage like the one which changed the 
Mississippi River?

Response #:  1 of 1
Author:      Ronald Winther
Text:        The "New Madrid" earthquakes of 1811-1812, named for the town of 
New Madrid, in southeast Missouri, are what you read about.  This series of 
three strong (estimated at over 8 on the Richter scale) quake events with 
numerous after-shocks was one of the most violent to occur in U.S. history.  
The shocks were felt from Canada to New Orleans, and as far east as Boston, so 
were certainly strongly felt in Illinois.  (You may recall that there was a 
prediction that a massive earthquake would occur in December 1990 centered in 
the New Madrid area following a moderate quake there in September of that 
year.  It received a huge amount of media coverage and, luckily, failed to 
come true.)  For recent quakes, the best I could come with is a Department of 
Commerce publication entitled "Earthquake History of the United States," which 
has data up through 1980. It lists, for the decade 1971-1980:  Sept. 15, 1972 
(3.7); April 3, 1974 (4.7); June 5 (4.0), 1974; and Dec. 5, 1978 (3.5) as the 
dates of earthquakes having epicenter in Illinois.  (The number in parenthesis 
after each date is the Richter scale of the quake).  Of these, all but the
first were centered in southern Illinois (the most common locale for 
occurrence because of its nearness to the New Madrid fault); the '72 quake 
caused minor damage in Amboy, Holcomb, and Rock Falls in northern Illinois.  
None of these quakes came anywhere close to the 1811-12 quakes.  The Richter 
scale is logarithmic; the energy released in the 1811-12 quakes was at least 
hundreds of thousands of times more than the severest of the "modern" quakes 
listed above.