It's hard to see the big picture when the ground keeps shifting beneath your feet.
But three Princeton researchers — associate professor of civil and environmental engineering George Deodatis, associate professor of architecture Guy Nordenson and civil engineering graduate student Michael Tantala — accomplished just that this past semester. By using a computer program to simulate earthquakes, Deodatis, Nordenson and Tantala completed a study that determined the effects a medium-size earthquake might have on every building in Manhattan.
According to Tantala, though many residents of New York may believe an earthquake will never hit the Big Apple, it is nevertheless a real possibility. So the researchers, in partnership with the New York City Consortium for Earthquake Loss Mitigation and the Federal Emergency Management Agency, used a computer code called HAZUS and information on soil types, building structures and population in the city to help understand the physical and financial damages that could result from an earthquake centered near New York.
HAZUS, which stands for Hazards U.S., was developed by FEMA in 1997. It is the first standard method of evaluating loss from natural disasters, said Tantala. The program is run on a PC just like the ones lined up in campus computer clusters and analyzes data to produce a comprehensive picture of the aftermath of an earthquake.
"You don't need a supercomputer to do this," Deodatis noted. Instead, utilizing their computers, the researchers fed existing data for a comprehensive set of factors into the computer code, starting from the ground and working up. They used information about soil types and about how the ground underneath Manhattan would move in the event of an earthquake. Afterwards, they used engineering techniques to determine how the buildings on top of the soil would react to the movement.
As part of the study, they even sent undergraduate researchers into the city to photograph individual buildings, said Nordenson. And by including census information in their calculations, the researchers were able to tell how an earthquake might affect the people of the city themselves.
Deodatis, Nordenson and Tantala's results present a comprehensive view of the damage an earthquake would cause in Manhattan. It delineates possible structural destruction, human casualties, financial losses from building repairs and lost wages and the stress that would be placed on emergency services such as hospitals.
Some of Manhattan's greatest strengths — its large population and high concentration of capital, particularly bulding structures — make it particularly vulnerable to earthquake damage. Though the city does have a seismic building code, the city's vulnerabilty is compounded by a general lack of preparedness.
.. Nordenson compared the predicted effects of an earthquake in Manhattan with the 1989 earthquake in San Francisco. "You had very focused areas of severe damage surrounded by large areas where there was no damage at all," he said. "It's a bit surreal."
Areas of Manhattan with softer soil, such as the edges of the island, would experience the most damage, Nordenson noted. Meanwhile, high-rise buildings are likely to sustain the least damage in an earthquake because of the nature of their steel-frame construction and the more solid soil on which they are built.
"If you look at the skyline," Nordenson said, "Where you have the skyscrapers, that's where you have the good soil."
During an earthquake, the areas of softer soil in Manhattan could be as dangerous as any given spot on a west coast fault line. "If you're sitting on Telegraph Hill on top of a good rock, you'd be better off than on a soft soil area in Manhattan," Nordenson said.
While the New York area does not experience earthquakes quite as often as California, even a moderate earthquake in the area could have serious consequences. "It's a high-risk, low-probability event," said Deodatis.
An earthquake of magnitude seven, for example, would make skyscrapers shake and shed their cladding, causing about 54 billion dollars worth of damage and killing or injuring about 300 people, according to Tantala. But an earthquake of this size is expected to occur once every 150,000 years, he said, and thus is not an immediate concern.
But in 1884 an earthquake of about magnitude 5 did shake the city. Earthquakes of this strength are what the city should be worried about, Tantala suggested. Statistically, earthquakes of this size occur once every 2,500 years in New York. "It seems like a trend," he said. "It's been overdue."
Smaller tremors are a another real concern. An earthquake registering about 2.5 on the Richter scale shook the area around 85th Street and Second Avenue in the Upper East Side last month. Though few people felt the small earthquake, it brought to public view the city's vulnerabilty to earthquakes damage.
But the researchers' intent is not to whip New Yorkers into a frenzied panic or make them fear that the 'big one' is around the corner. After all, said Nordenson, "The likelihood is that I'll be killed by something else before I get killed by an earthquake."
Rather, they hope to raise public awareness about earthquakes in the New York metropolitan area and help emergency services become better prepared to face them. To that end, Deodatis, Nordenson, and Tantala will present their report to NYCEM this week.
After this week, the Princeton researchers plan to continue to investigate the effects of earthquakes and other natural disasters on the New York region. But the next step towards preparing the Big Apple for the next earthquake will have to be taken by the politicians.
"We're putting [the information] into the hands of those than can use them," Tantala noted.
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