When the `Big One' finally comes, it may well hit someplace other than California. While that state has more earthquake activity, much of the Midwest is at risk for large -- and potentially more dangerous -- earthquakes
by William F. Allman
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Three of the nation's largest earthquakes ever have occurred not on the West Coast but in the center of the country. In December of 1811 and January and February of 1812, an area near the town of New Madrid in southeastern Missouri was rocked with successive earthquakes estimated to range from 8.4 to 8.8 on the Richter scale -- that is, nearly 100 times as mighty as the quake that hit Los Angeles last week. The Mississippi River flowed backward and changed course; bells rang in Boston church towers, and chandeliers shook in the Capitol in Washington, D.C.
The quakes that occur in the Midwest are unusual. Unlike the temblors that rattle the Pacific coastline, they involve no shuffling of the Earth's massive crustal plates along a fault line. But a tremendous pressure does build up as the sea floor spreads from the middle Atlantic and slowly drives the North American plate toward the Pacific. The resulting east-west pressure apparently causes the crust to fracture.
If such a temblor does hit the Midwest again, it may have far more damaging consequences than the L.A. quake. The solid crustal plate beneath the Midwest transmits a quake's energy far more efficiently than do the faults in California, meaning that damage would be more widespread. And Midwestern cities are simply not engineered to withstand such shaking and rattling: According to a federal study, a quake like last week's, but centered in Memphis during daylight hours, would kill nearly 3,000 people -- a quarter of them in schools, which tend to be older buildings.
Major Quakes in the U.S. Year Richter Scale Deaths
