Parts of LI shaken by 3.9-magnitude earthquake

Yes, Long Island, that was an earthquake Tuesday.

From Massapequa to Montauk, people felt the earth move under their feet when a 3.9-magnitude earthquake struck just before 11 a.m. It was centered nearly 100 miles southeast of the Island, deep in the Atlantic Ocean, according to the U.S. Geological Survey.

Some thought it must have been a tractor-trailer rumbling by. Others were convinced it was the sound of construction work. Temblors are infrequently felt on Long Island, so Tuesday's morning jolt caught many off guard.

It occurred at 10:49 a.m., about 80 miles southeast of Quogue and Southampton. The epicenter was at a depth of 4.1 miles, according to government scientists. "In terms of feeling it, I'd say that the people who felt this one haven't felt one in a couple of decades," said Daniel Davis, a geology professor at Stony Brook University, referring to all of Long Island feeling the quake.

No injuries or damage were reported.

Geologists said the earthquake did not appear to be centered on a known fault and occurred underneath thousands of feet of sediment.

Experts said the quake was likely caused by pressure built up over time causing a rupture about a half-mile long. Unlike larger temblors in areas like California or Haiti, where tectonic plates meet, Tuesday's earthquake occurred in a geologically stable area, experts said.

The metropolitan area will never be known as earthquake country, but ancient faults - stress points in bedrock - still exist and occasionally rupture, experts said. The U.S. Geological Survey's website reported that more than 900 people - mostly from Nassau and Suffolk counties - reported feeling the earthquake via an e-mail reporting system as of Tuesday night. People reported feeling the quake as far away as Vermont and West Virginia.

In Suffolk County, Rose Swezey, 55, of Water Mill, near Southampton, was looking out of an upstairs window of her home when she felt shaking that lasted about 15 seconds.

"Nothing fell, but there was a really heavy vibration," Swezey said. "It was just things vibrating - the lamp shade, that kind of thing."

Don Blakeman, a geophysicist with the U.S. Geological Survey in Reston, Va., said Long Island is fortunate that the earthquake's epicenter was at sea, and that the tremor sparked only slight shaking and no damage. Most earthquakes in the Northeast are centered on land.

Long Islanders last felt earthquake rumbles in June when a 5.0 temblor struck north of Ottawa. Office workers in Huntington said they felt the shaking.

Mary MacElveen, of Sound Beach, said she felt an aftershock two hours after Tuesday's earthquake.

"It felt like a noisy truck going down the street," MacElveen said. "The only different was I heard the house creaking - a lot."

Southampton Town Police Sgt. Andrew Ficurilli was in the communications room of police headquarters off Route 24 when he felt something unusual.

"We all of a sudden felt sort of a rumble in the building and we really didn't know what it was," he said. "We thought maybe there were some construction going on. We were curious about what it was; we really weren't thinking earthquake," he said.

With Michael Amon and Bill Bleyer

Other earthquakes felt on Long Island

Oct. 19, 1985. Centered in upstate Ardsley; 4.0 earthquake sent shock waves from eastern Pennsylvania to southern Canada; recorded as the strongest in 50 years.

April 20, 2002. Hit 15 miles southwest of Plattsburgh; 5.1 quake felt in Wantagh; tremors felt from Maine to Maryland.

June 22, 2010. Hit just north of Ottawa, Canada; 5.0 quake rattled buildings from upstate New York to Vermont in the U.S.; felt by office workers in Huntington.