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Under the world's greatest cities, deadly plates

As Hough notes in her book "Predicting the Unpredictable," the successful prediction of earthquakes was an official government mandate in Mao Zedong's China, but no one foresaw the killer quake that took at least 240,000 lives in Tangshan in 1976.

Port-au-Prince had not been hit with a major quake since the days of French rule in the 18th century. Only in recent years have scientists mapped the fault that runs near the city.

"Just the beginning of work had been done. But enough was known that it could produce a big earthquake," said Carol Prentice, a geologist with the U.S. Geological Survey. "We knew it would be bad, but I didn't imagine that it would be this bad."

Time bombs

Prentice had been to the island of Hispaniola and had studied a different, roughly parallel fault called the Septentrional, which runs along the island's northern edge. It had been difficult getting into Haiti, she said, so she and her fellow scientists focused their work on the Dominican Republic. That fault is another time bomb, threatening the Dominican city of Santiago, with a population of more than 1 million, Prentice said.

The entire Caribbean is seismically active. So is much of Central America. The next Big One could be on the isthmus of Panama, where Panama City sits just six miles from a major fault that hasn't ruptured in four centuries, said Mary Lou Zoback, a seismologist who works for the California-based Risk Management Solutions.

Or the next catastrophe could be in Caracas, Venezuela, where millions of people live in poverty near a boundary of two tectonic plates, including the one that created the fault that broke in Haiti. The last catastrophic quake was 198 years ago. Zoback said that relief groups have donated bricks to poor people in Caracas to help them build homes but that unreinforced brick dwellings are death traps in an earthquake.

Another seismic bull's-eye is Mexico City, which sits on the worst possible soil, a drained lake bed that will intensify seismic waves. The city also is in a basin in the mountains, which essentially traps the seismic waves. The devastating earthquake of 1985, which killed about 10,000 people, was centered hundreds of miles away but managed to ring Mexico City like a bell.

Earthquakes can turn up closer to home than many Americans realize. Several major tremors have been recorded off the East Coast, including near Newfoundland in 1929 and Boston in 1755. Charleston, S.C., had a quake in 1886 that killed 60 people. Hough, of the USGS, said it might be that all three earthquakes were associated with the edge of the continental shelf and that any coastal city, including Washington, could get rattled by a quake someday.

Another hazard is right in the Mississippi River valley. Memphis is close to the New Madrid fault, which caused powerful earthquakes in 1811 and 1812.

By some measures, the American city at greatest risk of a disastrous earthquake is New York.

Although New York City is rarely thought of as earthquake country, the region experiences many small tremors that indicate that larger ones are possible. The good news is that a magnitude-6 earthquake should happen only every 670 years or so. A magnitude-7 tremor should happen every 3,400 years. That's the calculation by scientists at Columbia University who studied 383 much smaller tremors recorded in the New York area from 1677 to 2007.

The bad news is that there is a massive amount of infrastructure built without earthquakes in mind.

"A lot of old brownstones -- they crumble well," Zoback said.

Mitigating destruction

Urbanization is a steady process. In the next half-century, the planet will add about 5 billion people and build about 1 billion housing units, Bilham estimates. The question is whether those people will live in buildings designed for a sometimes shaky world.

Brian Tucker, an earth scientist who leads GeoHazards International, said 10 percent of the money going to help Haiti rebuild should be dedicated to mitigating the destruction in earthquakes. But he also knows from many years of sounding warnings about possible earthquakes that people tend to be complacent about catastrophes that have yet to happen.

"People who advocate diet and exercise are chumps, and heart surgeons are heroes," Tucker said.

Bilham said he would like to see the United Nations develop a building-inspection program akin to its efforts to look for banned nuclear, biological and chemical weapons. Zoback, likewise, is impatient for action that could save lives:

"We know where the problems are. We know what to do. We know how to fix it. We just need the political will."

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