New Madrid Fault Shakes More Often Than Previously Believed

February 2003

A new U.S. Geological Survey (USGS) report estimates that the chance that a major earthquake will strike the New Madrid fault region (Illinois, Missouri, Kentucky and Tennessee) sometime in the next 50 years may be as much as 10 percent, up from previous estimates of three to four percent. The USGS report is based on studies that the New Madrid fault zone has major quakes every 500 years or so.

The risk is one factor for building code developers and building planners to consider, according to the USGS. "To make any decisions about how to deal with earthquakes, you need to know something about the amount of shaking you may get and how often it occurs," reports geologist Eugene Schweig, coordinator of the USGS earthquake hazards program for the central United States. "What the building code authorities do with that information is an economic decision."

A series of huge quakes struck the region from 1811 to 1812, causing the Mississippi River to flow backward and church bells to ring in Boston. The zone has produced small-to medium-size earthquakes since then. Geologists find it difficult to predict when the next major earthquake (magnitude 7.5 or larger) might happen. Researchers have found evidence in the geological record, however, that the 19^th century quakes were part of a larger pattern, stretching into prehistory.

Link to the press release for the report

Link to the fact sheet (PDF) for the report

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