(MENAFN- The Peninsula) The Washington Post
New York, USA: A 4.0-magnitude aftershock was recorded in northern New Jersey on Friday evening, a little more than seven hours after a 4.8-magnitude earthquake in the same area produced tremors that were felt in New York City and as far away as Maryland and Massachusetts.
The aftershock occurred around 6 p.m. local time, roughly six miles below the Earth's surface near Gladstone, N.J., according to preliminary data from the U.S. Geological Survey.
The tremors sent ripples throughout the surrounding area.
Within minutes, New York City's emergency notification system warned residents to "remain indoors and to call 911 if injured” after reporting "shaking in our facility.”
No injuries or fatalities had been reported by Friday evening.
Government agencies were searching for potential structural damage up and down the East Coast after the first quake, which briefly disrupted air-traffic control, slowed train service and jolted millions of Americans out of their daily routines.
The earthquake Friday morning, which hit at 10:23 a.m. Eastern time, had a stronger magnitude than usual for the East Coast. It struck just under three miles below the surface near Whitehouse Station, N.J., about 50 miles from Manhattan and eight miles from Gladstone, the U.S. Geological Survey reported.
"We thought something had exploded,” Tom Reilly, 73, of Lebanon Township, N.J., told The Washington Post by phone.
He was near the epicenter, picking up pizzas, when the ground began moving.
"That's the only thing that could cause something like that in New Jersey that we could think of,” he added.
The temblor was felt across a large swath of the eastern United States from Maryland to Connecticut, according to the USGS, including in Baltimore, Philadelphia and Boston.
About five seconds of slight shaking was felt in Cape Cod, Mass., and a few people reported it in southern Maine.
Six small aftershocks occurred between 11:30 a.m. and 2 p.m., ranging in magnitude from 1.8 to 2.2, according to the USGS.
Additional aftershocks remained possible, with a high chance of an earthquake of less than 4.0 magnitude within the next week.
No extensive damage to buildings had been detected Friday afternoon, including in New York City, though assessments were still taking place.
There were no major effects in the nation's capital, D.C. officials said.
"We're taking this extremely seriously,” New York Gov. Kathy Hochul (D) said at a late-morning news conference.
Earthquakes tend to be felt across wider distances on the East Coast of the United States than on the West Coast formations in the east are denser, allowing shaking to easily transfer across hundreds of miles, according to the USGS.
Quakes regularly occur on the East Coast but are commonly weaker, on a magnitude of 1 to 3. Among the largest recent earthquakes was a 5.8-magnitude quake in central Virginia that was felt by millions in 2011.
Friday morning's quake shook coffee cups, disoriented drivers and interrupted meetings - including of the United Nations.
In Brooklyn, neighbors flooded into the street. Many mistook the sudden shaking for a rumbling plane or train.
"It just absolutely did not click for me that this was an earthquake,” said Lillian Ruiz, 36, a business consultant who was working from home in a quasi-industrial corner of Brooklyn's Gowanus neighborhood. "I thought, sinkhole. I thought, structural collapse. ... An earthquake just made no sense.”
The tremors caused Hector, a 24-year-old food deliveryman who declined to share his full name so that he could speak freely, to lose control of his bicycle, he told The Post.
He fell and scraped his cheek.
"In seriousness, I thought I maybe ate or drank something that made me high,” he said in an interview in Spanish.
From Mexico City, he said he was no stranger to earthquakes, but "I was unprepared for one to arrive on a Friday morning in Brooklyn. It's like a snowstorm coming to Miami.”
The earthquake briefly disrupted air-traffic control facilities in the busy New York airspace, the Federal Aviation Administration said, but the affected airports were back to normal operations within two hours.
Meanwhile, Amtrak restricted speeds on its trains throughout the Northeast and began track inspections.
Initial inspections didn't find damage to the New York City transit system, the police department's transit chief said.
Service was temporarily suspended on South Jersey's transit line, PATCO, before inspections were completed.
President Biden was briefed on the earthquake and spoke to New Jersey Gov. Phil Murphy (D), the White House said.
Murphy said the state's emergency operations center was activated after the quake, and a state police spokesman confirmed that there had been no reported injuries or fatalities.
The morning earthquake was felt in a meeting of the U.N. Security Council in New York, where cameras shook and proceedings paused as a murmur went through the room.
Many took to X, formerly Twitter, to confirm what they had just felt - and to joke about it.
"I AM FINE,” the account for the Empire State Building posted about a minute after the quake.
It also prompted a flurry of emergency calls from startled residents.
Like agencies elsewhere, the Philadelphia Police Department asked people to stop calling 911 unless they had an emergency.
The USGS originally reported the 4.8 quake near Lebanon, N.J., then adjusted the location to Whitehouse Station, a neighboring town in Hunterdon County.
It was not immediately clear what triggered the earthquake.
It occurred along the Piedmont, a plateau that runs along the east side of the Appalachian Mountains.
Because that formation contains relatively old, dense rock, its shaking spreads across hundreds of miles.
"The energy transfers pretty efficiently through those types of rocks,” David Wunsch, the Delaware state geologist and a University of Delaware professor, told The Post.
Any damage is likely to be minor and confined to areas near the epicenter, and could include small objects toppling over or, at worst, some damage to poorly maintained masonry, Wunsch said.
Whatever caused the quake, it is unlikely to be anything of great geologic significance, said Leslie Sonder, an associate professor of earth sciences at Dartmouth.
"It's noteworthy because people felt it, but in geologic terms, it's just one of many over time,” she said. "It has social significance, but its geologic significance, it's pretty generic.”
The part of northern New Jersey where the quake occurred contains what Wunsch called failed rift valleys - places where a continent began to split hundreds of millions of years ago, leaving fault lines behind.
"It may be some readjustment related to that,” Wunsch said.
Another potential cause could be tens of thousands of years in the making.
Since glaciers disappeared from North America, the loss of ice on top of the continent has been slowly causing the East Coast to sink.
That change in stress causes earthquakes over time, Sonder said.
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