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Time - Man of the Year
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1993-04-08
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THE WEEK, Page 33SOCIETYBig One for Big Mo?
The ground is stretching in Missouri: a big quake is just a
matter of time
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.
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.