News Center, Northwestern University

ILLINOIS — The New Madrid fault system does not behave as earthquake hazard models assume and may be in the process of shutting down, a new study shows.

A team from Northwestern and Purdue universities analyzed the fault motion for eight years using global positioning system measurements and found that it is much less than expected given the 500- to 1,000-year repeat cycle for major earthquakes on that fault. The last large earthquakes in the New Madrid seismic zone were magnitude 7-7.5 events in 1811 and 1812.

Estimating an accurate earthquake threat for the area, which includes parts of Illinois, Indiana, Tennessee, Arkansas and Kentucky, is crucial for the communities potentially affected, said Eric Calais, the Purdue researcher who led the study. The research team included said Seth Stein, the William Deering Professor of Earth and Planetary Sciences in the Weinberg College of Arts and Sciences at Northwestern.

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