One of the strongest earthquakes recorded on the east coast of the United States has cracked the iconic Washington monument and sent thousands of workers fleeing skyscrapers in New York.
The magnitude-5.8 quake, which struck just before 2pm local time on Wednesday, forced evacuations of the Pentagon, the US Capitol and Washington’s historic monuments.
Damage was not catastrophic and there were no immediate reports of casualties.
The eastern seaboard rarely experiences larger earthquakes, and many workers were bewildered – and feared the worst – as their desks swayed violently and the ceilings and walls pitched and shook with fearsome force.
“I was in the street when the ground shook and I looked up to see the building shaking like a tuning fork,” a stunned Mary Daley told Agence France-Presse in New York City.
Thousands of workers fled office buildings and poured into the streets of Manhattan to be herded by police towards open areas, trying in vain to use overloaded mobile phone services to contact loved ones.
The earthquake came less than three weeks before the 10th anniversary of the September 11 al-Qaeda attacks, and in both Washington and New York it immediately triggered fears of something more sinister than a natural disaster.
Workers in the Empire State Building spilled into the streets, some having descended dozens of flights of stairs.
“I thought we’d been hit by an aeroplane,” said one worker, Marty Wiesner.
In Washington, engineers found a crack near the top of the Washington Monument, presumably caused by the quake, while the National Cathedral lost part of its towering neo-Gothic spires and suffered cracks in its flying buttresses.
National Park Service spokesman Bill Line said the stone obelisk monument will be closed indefinitely to keep the public safe.
The US Geological Survey said the quake was centred about 65 kilometres northwest of Richmond, Virginia, and 135 kilometres from Washington.
The quake, which lasted 20-30 seconds and had an epicentre six kilometres under the small central Virginia town of Mineral, was felt as far away as Boston and even in parts of eastern Canada.
In Mineral, masonry was crumpled all over town, many windows were broken and some chimneys cracked but church bell towers were still in place.
The nearby 1800-megawatt North Anna nuclear power station declared an alert after losing electricity from the grid, but its safety systems kicked in and it was soon operating normally, officials said.
The Pentagon, the world’s biggest office building located across the River Potomac from the capital, ordered a brief evacuation, which was carried out calmly. Several hundred people streamed out of the building and officials said there was no damage other than a ruptured water line.
US President Barack Obama was not at the White House and did not feel the quake as he was playing golf some 800 kilometres away in tranquil Martha’s Vineyard off the coast of Massachusetts.
Briefed by his aides, Obama was told “there are no initial reports of major infrastructure damage, including at airports and nuclear facilities,” said deputy White House spokesman Josh Earnest.
In a bizarre legal twist, the quake prompted the early closing of the Manhattan courthouse offices, meaning former IMF chief Dominique Strauss-Kahn had to wait until Wednesday to collect his passport and leave the country after sexual assault charges against him were dropped.
Scientists said the harder, more brittle quality of the ground explained why rare tremors on the US east coast are often felt over an area many times bigger than those of a similar magnitude on the more quake-prone west coast.
It was the largest quake in Virginia since May 1897, when a 5.9 quake struck near the state’s western edge.
The last quake of equal power to strike the east coast was in New York in 1944.
The largest East Coast quake on record was a 7.3 that hit South Carolina in 1886.
The quake hit as emergency officials warned that Hurricane Irene, which was roaring through the Atlantic, may strike the eastern US seaboard this weekend.