NEW MADRID, MISSOURI
In the United States, most earthquakes occur along
the active plate boundaries in California, Oregon, Washington, and
Alaska. If you live in one of these states, you may have felt an
earthquake. However, several of the largest earthquakes ever recorded in
the United States occurred in the Midwest, far from any plate boundary.
These earthquakes took place in an area called the New Madrid Fault
Zone, named after the town of New Madrid, Missouri. Over a three-month
period in the winter of 1811 to 1812, the New Madrid Fault Zone was
struck by three huge earthquakes estimated to be greater than magnitude
8.0. Aftershocks were felt in the region for more than a year. These
included seven aftershocks between magnitude 7 and 8, ten between
magnitude 6 and 7, and eighty_nine between magnitude 4 and 5. Many
aftershocks were strong enough to ring church bells on the east coast of
the United States.
Modified Mercalli Scale, based on maps in W. Atkinson, 1989, The
Next New Madrid Earthquake, Southern Illinois, University Press.