NEW YORK — The ground rumbled Friday beneath New York City, home to famous skyscrapers such as the Empire State Building and One World Trade Center. Although buildings that can reach more than 100 stories appear particularly vulnerable to earthquakes, engineering experts say skyscrapers are built with enough flexibility to withstand moderate tremors.
The 4.8 magnitude earthquake struck about 45 miles (72 kilometers) west of the New Jersey city Friday morning. The aftershocks continued, with a magnitude 2.5 earthquake hitting the area on Saturday morning. But no major damage was reported to the city’s public transportation system or to its 1.1 million buildings.
Operators of the iconic 103-story Empire State Building posted “I AM FINE” to the building’s X account on Friday.
New York’s skyscrapers are generally built to withstand winds and other shocks that are much larger than the earthquakes typically seen on the East Coast, says Elisabeth Malch, president of Thornton Tomasetti, a New York engineering firm that major has done work on the Empire State Building. , Chrysler Building and the Brooklyn Bridge, among other major city landmarks.
“The earthquake we are designing for is one that is unlikely to happen. It’s a millennial event,” she explained. “So we don’t expect this to happen more than once every thousand years.”
Skyscrapers, by design, are less susceptible to the ground-shaking action of earthquakes than shorter structures, because they are made to sway very slowly and slightly to protect themselves from powerful hurricane-force winds, Malch said.
“Taller buildings are simply more flexible because they are designed for the push and pull of the wind, which has a greater effect on tall buildings than the push and pull of an earthquake,” she explained. “So regardless of when it was designed, the wind is constantly testing them. It is a double check whether they are strong enough and flexible enough to withstand earthquakes.”
Even the oldest skyscrapers are necessarily made of high-strength concrete and steel to withstand the gravitational loads on the massive structures, added Ahmad Rahimian, an executive vice president at engineering firm WSP Global, who was involved in the construction of One World Trade. Center, the tallest building in this hemisphere, and The Shard in London, the tallest building in Europe.
“Tall buildings can be one of the safest places during an earthquake,” he said.
More modern high-rise homes also have dampers on their roofs that can compensate for the fluctuations and help absorb the shock of extreme events, says Borys Hayda, managing director at DeSimone Consulting Engineering, a New York firm that has been involved in renovating some of the tallest buildings in Manhattan. hotels, theaters and other monumental buildings.
“Even though there is only a small chance of earthquakes here in New York, we as engineers have to design for all types of potential risks,” he said.
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Associated Press writer Michael Hill contributed.