(New York) The ground rumbled Friday beneath New York City, home to famous skyscrapers like the Empire State Building and One World Trade Center. Although buildings taller than 100 stories may seem particularly vulnerable to earthquakes, engineering experts say skyscrapers are built with enough flexibility to withstand moderate shaking.
Friday morning’s 4.8 magnitude earthquake occurred about 45 miles (72 kilometers) west of the New Jersey city. The aftershocks continued, with a 2.5 magnitude earthquake on Saturday morning. But no major damage has been reported to the city’s transit system or its 1.1 million buildings.
The operators of the iconic 103-story Empire State Building posted “I AM OKAY” on the building’s account on the social network X on Friday.
New York’s skyscrapers have generally been built to withstand winds and other impacts far greater than the earthquakes typically seen on the U.S. East Coast, said Elisabeth Malch, managing director of Thornton Tomasetti, a New York engineering firm that has completed major work on the Empire State Building, the Chrysler Building and the Brooklyn Bridge, among other major city landmarks.
“The earthquake we are designing (the buildings) for is unlikely to occur. It’s an event that happens every thousand years, she explained. So we don’t expect it to happen more than once every thousand years. »
Skyscrapers, by design, are less susceptible to earthquake action than shorter structures, because they are designed to sway very slowly and lightly to protect against powerful hurricane-force winds , said M.me Malch.
Taller buildings are simply more flexible, as they are designed to resist the push and pull of wind, which has a greater effect on tall buildings than the push and pull of a earthquake, she explained. So, regardless of when they were conceived, the wind continually tests them. It’s a double check that they are strong enough and flexible enough to withstand earthquakes.
Elisabeth Malch, Managing Director of Thornton Tomasetti
Even the oldest skyscrapers are, by necessity, made of concrete and high-strength steel to withstand the gravitational load exerted on massive structures, added Ahmad Rahimian, executive vice president of engineering firm WSP Global which participated in the construction of One World Trade Center, the tallest building in this hemisphere, and The Shard in London, the tallest building in Europe.
“High-rise buildings can be one of the safest places in an earthquake,” he argued.
More modern skyscrapers also have shock absorbers on their roofs that can balance sway and help absorb any shock from extreme events, said Borys Hayda, managing director of DeSimone Consulting Engineering, a New York firm. involved in the renovation of some of Manhattan’s major hotels, theaters and other iconic buildings.
“Even though there is only a small possibility of earthquakes here in New York, we as engineers must design for all types of hazards,” he said.