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- THE WEEK, Page 33SOCIETYBig One for Big Mo?
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- The ground is stretching in Missouri: a big quake is just a
- matter of time
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- Three of the most powerful earthquakes ever to hit the U.S.
- -- each topping 8.0 on the Richter scale -- struck near the town
- of New Madrid, Missouri, in the early 1800s. It is hardly an
- obvious location. The theory of plate tectonics says quakes
- should happen most often along the edges of crustal plates,
- pancakes of rock a few score miles thick and thousands of miles
- across, which carry the continents on their backs as they slide
- across the semimolten mantle below. The plates ride over each
- other or grind together, and the earth shakes. But New Madrid is
- right in the middle of a plate, a place where earthquakes are
- generally not seen.
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- Unfortunately, scientists believe, the town has the bad
- luck to sit atop a weak spot, and as the plate moves, it
- stretches -- and sometimes cracks. Now a report in Science bears
- out that belief: a new survey reveals that stresses in the earth
- have been rising sharply in the area since the 1950s. The
- amount of change points to a big quake in about 1,000 years,
- which is roughly the historical average indicated by the
- geological evidence. But that is just an average. It could also
- happen tomorrow.
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