The earth rumbled Friday beneath New York City, home to famous skyscrapers such as the Empire State Building and One World Trade Center. While buildings that can exceed 100 stories may seem particularly vulnerable to earthquakes, engineering experts say skyscrapers are built with enough flexibility to withstand moderate shaking.
Friday morning’s magnitude 4.8 quake was located about 45 miles (72 kilometers) west of the city in New Jersey. The aftershocks continued, with a magnitude 2.5 quake on Saturday morning. But no serious damage was reported to the city’s public transportation system or its 1.1 million buildings.
Operators of the iconic 103-story Empire State Building posted “I’M GOOD” on the building’s X account on Friday.
New York’s skyscrapers were generally built to withstand winds and other impacts much stronger than the earthquakes typically seen on the East Coast, said Elisabeth Malch, managing principal at Thornton Tomasetti, a New York engineering firm that has done major work on the Empire State Building. , Chrysler Building and the Brooklyn Bridge, among other important city landmarks.
“The earthquake we plan for is unlikely to happen. It is a thousand-year event,” she explained. “So we don’t expect it to happen more than once every thousand years.”
High-rise buildings, 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 a hurricane’s powerful, violent winds, Malch said.
“Taller buildings are simply more flexible because they are designed for the push and pull of wind, which has a greater effect on tall buildings than the push and pull of an earthquake,” he explained. “So regardless of when they were designed, the wind continually tests them. It’s a double check that they are strong and flexible enough to handle earthquakes.”
Even the oldest skyscrapers are, by necessity, made of high-strength concrete and steel to resist the gravitational load on the massive structures, added Ahmad Rahimian, executive vice president of the engineering firm WSP Global involved in the construction of One World Trade. Center, the tallest building in this hemisphere, and The Shard in London, which is the tallest building in Europe.
“Skyscrapers can be one of the safest places you can be in an earthquake,” he said.
Most modern skyscrapers also have shock absorbers placed on the roofs that can balance the sway and help absorb any shocks from extreme events, added Borys Hayda, a principal at DeSimone Consulting Engineering, a New York firm involved in the renovation of some of the major Manhattan buildings. hotels, theaters and other historic buildings.
“Even though there is only a small chance of earthquakes here in New York, we as engineers need to design for all types of potential hazards,” he said.
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Associated Press writer Michael Hill contributed.