Geological Survey said, and homes and businesses were shaken from Canada's capital in Ottawa on south to an arc of U.S. states.
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No damage or major injuries to report, but people from as far away as Cleveland and Michigan report feeling it.
New York City Emergency Management officials say they are receiving reports of tremors from multiple locations in the city and that the Fire Dept is investigating a number of reports of shaking buildings.
The epicenter of the Wednesday afternoon earthquake was more than 400 miles away in Canada, but the tremor rattled employees in Hackensack at one Bergen County Plaza.
The 5.0 quake also jolted workers in Lower Manhattan and Downtown Brooklyn.
The quake was felt most strongly be people along the Ontario-Quebec border.
Canadian TV was broadcasting a press conference when the earth began shaking.
Buildings in Ottawa sustained visible damage, and within moments, people posted photos on Twitpic of crowds standing on the streets in disbelief.
Hundreds of employees were evacuated from an office building in Lyndhurst for more than two hours when people on the fifth and sixth floor reported shaking.
"Everyone got dizzy all at once so we knew something happened," said Rulin Estivalletti, an employee.
"I felt a little queasy and dizzy and then it went away. I thought it was just me getting old," said Daniel Seidman, an employee.
Powerful earthquakes in Canada are quite rare, but Columbia University seismologist Won-Young Kim says it's not surprising that the quake's effects would be felt so far away.
"If you have solid material it travels and then if you hit soft material they will shake locally. It's not everywhere the same feeling, soft sediment will feel more, people on bedrock will not feel much," Dr. Kim said.
Other states that reported feeling tremors were Indiana, Michigan, Ohio, Pennsylvania, West Virginia, Vermont, New Hampshire, New Jersey and New York.
The epicenter of the quake was in Quebec, about 23 miles (38 kilometers) north of Cumberland, Ontario, on the Ottawa River, the USGS said.
The agency said the quake occurred at a depth of about 12 miles (19 kilometers) at 1:45 p.m. EDT (1741 GMT). The agency initially said the quake had a 5.5 magnitude, but later reduced it to a magnitude-5.0.
The tremors, which lasted about 30 seconds, rattled buildings in Ottawa and Toronto, as well as government offices across the Ottawa River in Gatineau, Quebec.
The Parliament building in Ottawa was evacuated, with workers sent home while the building was inspected. Workers also left buildings in Toronto.
The quake came just ahead of the weekend summit of G-20 and G-8 world leaders in Toronto and Huntsville, Ontario.
Melanie Lauzon, a Liberal member of Parliament, said her first thought was that Ottawa had been hit with "with a very large car bomb," since the quake struck on the eve of the summits.
Conservative Senator Lowell Murray said the massive chandeliers of the upper chamber of Parliament began swaying during a mundane debate on energy issues.
"Initially we thought it might have been an airplane crashing into the building," Murray said. "But we were standing around wondering what was going on. And I quickly realized it was an earthquake. And then everybody started shouting 'Out, out, out."'
The damage appeared to be concentrated in Gracefield, Quebec, a tiny municipality of just over 2,300 not far from the epicenter of the quake, which was located about 37 miles (59 kilometers) north of Ottawa. Gracefield's residents ran through the streets as the buildings around them creaked and cracked, said town councilor Michael Gainsford.
At least seven buildings were damaged, Gainsford said.
Residents of a number of U.S. states in the Midwest and Northeast reported feeling the earthquake.
In Ohio, people reported the sound of plaster cracking in Cleveland and buildings in Cincinnati gently swaying.
In Cleveland, James Haselden says his office in a renovated 19th century brick building swayed and he heard plastic cracking but saw no damage.
The Pittsburgh Post-Gazette reported on its website that the Canadian quake was felt by some residents in the western Pennsylvania area.
In Michigan, residents from suburban Detroit to Port Huron and Saginaw reported feeling the earthquake.
Detroit police spokeswoman Yvette Walker told The Associated Press that police personnel on the upper floors of the downtown headquarters building reported feeling the quake.
In New York state, people from Buffalo to Albany and north to Massena on the St. Lawrence River said pets were startled and plates rattled when the quake hit.
New York City officials said police received emergency calls from all over the city about shaking buildings, but there were no reports of damage.
David French, 53-year-old state worker from Cicero, New York, said he was at his computer inside his home near Syracuse when he felt his chair shake.
"I thought the chair was breaking or something," he said. "I looked over and my filing cabinet was moving."
The quake prompted several calls to state police in the Adirondacks area.
"A little shake, nothing too big," is how Trooper Mark Revette described the temblor. "It happens. We get a couple of these a year."
Kellie Tassone, 40, was at home on Oneida Lake in Cicero.
"My dog picked his head up just before it happened and kind of looked at me," she said. Then the sliding door started to rattle "and the house was shaking."
The USGS said the two largest quakes in western Quebec occurred in 1935 at magnitude-6.1 and in 1732 at a magnitude of 6.2, when it caused significant damage in Montreal.
The agency said earthquakes cause significant damage in the region about once a decade. Smaller earthquakes are felt three or four times a year.
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ON THE NET:
http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/us2010xwa7.php#details
The associated press contributed to this report
