The U.S. Geological Survey at first estimated the 7:12 p.m. quake as a 4.6 magnitude, but later downgraded that to 4.0. The epicenter, about 3 miles west of Hollis Center, Maine, is about 3 miles deep. That location is about 20 miles west of Portland.
About 10 miles away in Waterboro, about 20 customers and staff at Waterboro House of Pizza ran outside when they heard a loud bang and the building shook.
"It was loudest bang you ever heard in your life. We actually thought it was an explosion of some type," said owner Jessica Hill. "The back door and door to the basement blew open."
In nearby Saco, Sue Hadiaris said, "The whole house shook. It felt like a train was coming right through the house. It was very unnerving because you could feel the floor shaking. There was a queasy feeling."
Afterward, Hadiaris called her 15-year-old niece in Falmouth to make sure she was safe. "She said, 'We can cross that off our bucket list. We've lived through an earthquake,'" Hadiaris said.
Lynette Miller, a spokeswoman for the Maine Emergency Management Agency, said her dogs started barking several seconds before the quake. "It was several seconds of good shaking but nothing falling down," Miller said from her home in Readfield, about 60 miles north of Portland.
The Seabrook Station nuclear plant, about 63 miles away in New Hampshire, declared an unusual event - the lowest of four emergency classifications, but said it was not affected. The plant has been offline for refueling.
"There has been no impact at all to the plant from the earthquake and our refueling maintenance activities have not been affected," said Alan Griffith, spokesman for Next EnergyEra Seabrook Station.
Jim Van Dongen, public information officer for the New Hampshire Department of Safety said New Hampshire 911 got about 1,000 calls in the first hour after the quake, but they later dropped off. He said no major damage was reported.
Brief, but noticeable shaking was felt in downtown Boston and the surrounding area.
In Melrose, just north of Boston, Peter Ward said the shaking he felt seemed to last about four seconds. "It felt like a big gust of wind shaking the house. I don't want to overstate it, but the glass did rattle a little," he said.
Former Maine resident Victoria Brett, who also has lived in San Francisco, felt the quake in Northampton, Mass.
"At first, it felt like something slowly wiggling the outside walls of the house. Then the table and floor started vibrating. I looked around and the water in the glass flower vase looked like a wave pool. I knew right away it was an earthquake," she said.
Earthquakes are rare in New England but they're not unheard of. In 2006 there was a series of earthquakes around Maine's Acadia National Park, including one with a magnitude of 4.2 that caused boulders to fall from ledges onto Acadia National Park's loop road. One of the park's trails was closed for three years because of damage from the quake.
The strongest earthquake recorded in Maine occurred in 1904 in the Eastport area, near the state's eastern border with Canada, according the Weston Observatory at Boston College. With a magnitude estimated at 5.7 to 5.9, it damaged chimneys and brick walls and could be felt in Massachusetts and New Hampshire.
East Coast quakes are rarely strong enough to be felt over a wide area. A quake of magnitude 5.8 on Aug. 23, 2011, was centered in Virginia and felt all along the coast, including in New York City and Boston. Experts say the region's geology can make the effects felt in an area up to 10 times larger than quakes of similar size on the West Coast.