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What About the New Madrid Fault?

A major earthquake threat to Southern Illinois comes from the New Madrid fault zone, which runs from northeastern Arkansas to the southern tip of Illinois. Three of the largest earthquakes in U.S. history, all estimated to have exceeded magnitude 8.0, occurred along this fault in 1811 and 1812. The biggest was centered near the town of New Madrid, Mo., about 80 miles southwest of Carbondale as the crow flies.

Did those quakes form pseudotachylites? We can't know for sure, says geologist Eric Ferré, because thick layers of sediment still cover the places where the fault ruptured. "But if we drilled down through the fault zone, I am confident that the drill hole would intersect pseudotachylites," he says.

Unfortunately, because the fault is covered by those layers of sediment, it isn't very suitable for the type of early-warning system that Ferré envisions: engineers would have to drill down to the fault in order to place instruments. But faults in other places, such as California, would be good candidates.

--by Marilyn Davis, ed.

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