Yesterday, a rare earthquake left New Yorkers rattled and even a bit scared. So far there hasn't been any major damage reported from the 5.9 tremor, but it does raise an important question:
Can Manhattan's skyscrapers withstand a major earthquake?
The most obvious place to look for a foreshadowing of such a potentially disastrous event is Japan, which was recently hit by an 8.9 earthquake. Outside of the catastrophic death toll that resulted largely from an ensuing tsunami, Tokyo's skyscrapers remained standing. The structures, first erected in the late 60's, were built to survive the sort of violent tectonic activity endemic to the region. Here's footage of the buildings during the earthquake:
In essence, they bended, but didn't break. Many of Manhattan's tallest structures are designed to respond similarly, enabling them to give -- at least slightly -- as a way of coping with the force of powerful winds. Fortunately, this flexing also so happens to reduce the seismic forces in the event of an earthquake. You can think of it as a building's way of rolling with the punches to mitigate the impact.
And to prevent skyscrapers from swaying and oscillating too much as to lead to structural failure, they're bolstered with a sturdy central core and supportive bracing that often consists of diagonal steel beams (i.e. the Empire State Building). Some even feature modern modifications such as a tuned mass dampers, a spherical device designed to absorb the vibrations. The 915-foot tall Citicorp center, for instance, had a 410-ton concrete damper added after the fact as way of stabilizing the building.
A 5.8-magnitude earthquake centered on Fifth Ave. would send shattered glass cascading from skyscrapers, trigger fires and give New Yorkers a severe case of nerves, experts say.
"It wouldn't be something that would cause widespread devastation," said Dan Davis, a professor of geoscience at SUNY Stony Brook on Long Island. "But we do have a pretty old infrastructure."
Additionally, some older structures, such as brownstones, lack adequately reinforced masonry and may possibly crumble, according to a 2005 report from the New York City Area Consortium for Earthquake Loss Mitigation, a group comprised of concerned private and public officials. They also noted that buildings sitting on softer soil instead of being securely attached to solid bedrock were more likely to topple over. Areas like Chinatown and the Upper East side are particularly vulnerable.
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More innovative structures: