Tens of millions of people from Georgia to Canada were jolted Tuesday by the strongest earthquake to strike the East Coast since World War II. Three weeks before the 10th anniversary of Sept. 11, office workers poured out of New York City skyscrapers and the Pentagon, relieved it was nothing more sinister than an act of nature.
No deaths or serious injuries were reported.
Late Tuesday, the National Park Service said that engineers found a crack near the top of the Washington Monument, presumably caused by the temblor, and that the monument would be closed until engineers decide how to deal with it.
The White House said advisers had told President Obama that no major damage had been reported to the nation's infrastructure, including airports and nuclear facilities.
The U.S. Geological Survey said the earthquake registered magnitude 5.8 and was centered 90 miles southwest of Washington.
It was mild by West Coast standards. But the East Coast is not used to earthquakes of any size, and this one briefly raised fears of a terror attack less than three weeks before the 10th anniversary of Sept. 11.
"I thought I was having maybe a heart attack, and I saw everybody running," said Adrian Ollivierre, an accountant who was in his office on the 60th floor of the Empire State Building when the shaking began. "I think what it is, is the paranoia that happens from 9/1 1, and that's why I'm still out here -- because, I'm sorry, I'm not playing with my life."
Two nuclear reactors at the North Anna Power Station in Virginia's Louisa County, the same county as the epicenter, were automatically taken off line by safety systems, said Roger Hannah, a spokesman for the U.S. Nuclear Regulatory Commission.
At the Pentagon, a low rumbling built until the building itself was shaking, and people ran into the corridors of the complex. The shaking continued there, to shouts of "Evacuate! Evacuate!" The main damage to the building, the largest single work space for the federal government, came from a broken water pipe.
The Park Service closed all monuments and memorials on the National Mall, and ceiling tiles fell at Reagan National Airport outside Washington. Many nonessential workers in Washington were sent home for the day. The Capitol was reopened by late afternoon for people to retrieve their things.
The National Cathedral said cracks had appeared in the flying buttresses around the apse at one end. "Everyone here is safe," the cathedral said on its official Twitter feed. "Please pray for the Cathedral as there has been some damage."
In lower Manhattan, the 26-story federal courthouse, blocks from ground zero, site of the Sept. 11 attacks, began swaying, and hundreds of people streamed out of the building.
New York Police Commissioner Raymond Kelly was in a meeting with top deputies planning security for the upcoming anniversary when the shaking started.
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 airplane," said one worker, Marty Wiesner.
On Wall Street, the floor of the New York Stock Exchange did not shake, officials said, but the Dow Jones industrial average sank 60 points soon after the earthquake struck.
The Dow finished the day up 322 points.
Shaking was felt as far south as Charleston, S.C., as far north as Maine and as far west as Cincinnati and Atlanta. It was also felt on Martha's Vineyard, off the coast of Massachusetts, where Obama, taking summer vacation, was starting a round of golf when the earthquake struck at 1:51 p.m.
Obama led a conference call Tuesday afternoon on the earthquake with top administration officials, including his homeland security secretary and national security adviser.
Around Mineral, Va., a small town close to the epicenter, people milled around on their lawns, on sidewalks and parking lots, still rattled and leery of re-entering buildings.
All over town, masonry was crumpled, and the contents of store shelves were strewn on the floor. Several display windows at businesses in the tiny heart of downtown were broken and lay in jagged shards.
The last quake of equal power to strike the East Coast was in New York in 1944. The largest East Coast earthquake on record was a 7.3 that hit South Carolina in 1886.
The Virginia earthquake came a day after an earthquake in Colorado toppled groceries off shelves and caused minor damage to homes in the southern part of the state and in northern New Mexico.
Immediately after Tuesday's earthquake, the Federal Aviation Administration ordered planes at airports around the country to stay on the ground rather than fly to airports in New York; Philadelphia; New Jersey; Washington, D.C.; and Virginia where traffic was temporarily halted. Among major airports in the region, only New York's LaGuardia continued operations throughout the day.
By late afternoon, traffic at all the airports was returning to normal, although delays were expected into the evening.