Earthquake Rattles New York and New Jersey, but Does Little Damage

At a general store in New Jersey, near the epicenter of the earthquake, the sound was so loud that the staff thought a truck had crashed into the building.

Five miles away, at some riding stables, the ground shook so forcefully that it sent three horses galloping around the ring.

Within hours, a custom T-shirt shop in Manhattan was already selling a souvenir: a shirt emblazoned with, “I Survived The N.Y.C. Earthquake, April 5th, 2024.”

For most of the millions of people who felt the magnitude-4.8 earthquake that sent tremors from Philadelphia to Boston on Friday morning, it was a harmless novelty in a part of the country unaccustomed to seismic shaking.

But the rattling shook buildings in New York City and drove startled residents into the streets. Aftershocks continued throughout the day Friday, including one that measured 4.0 just before 6 p.m. and that was felt widely across New York and New Jersey.

Aftershocks would likely “continue for several days and even a week,” said Kishor S. Jaiswal, a research structural engineer with the United States Geological Survey. There is also a small chance that an earthquake of similar or even larger magnitude could occur during such a sequence, he said.

Officials in New York said they had been in touch with counties as well as nuclear facilities across the state, with no reports of damage aside from a gas leak in Rockland County. “Fortunately here in the state of New York, we are masters of disasters,” Gov. Kathy Hochul said. “We know how to handle this.”

Gov. Philip D. Murphy of New Jersey, who is out of the state at a conference, said in a televised interview that reports of structural damage were “de minimis.”

Based on data from the U.S.G.S., the earthquake, with an epicenter in Whitehouse Station, N.J., about 40 miles west of New York City, was the third strongest within 250 miles of the city since 1950.

Even as sirens could be heard across New York, the Police Department, Fire Department and Con Edison said they had no immediate reports of damage. Mayor Eric Adams, who was attending a gun violence prevention meeting at Gracie Mansion, said he did not even feel the earthquake and was informed of it by his staff members. “New Yorkers should go about their normal day,” he said at a midday news conference.

But the earthquake also revealed apparent shortcomings in New York’s emergency notification system, coming after the Adams administration has been criticized for a delayed response to floods and wildfire smoke. On Friday, beeping text alerts warning residents to stay indoors were received a half-hour or more after the earthquake hit. (In earthquake-prone areas like California and Japan, a network of seismic sensors detect shaking, so alerts can arrive seconds before the quake.)

Zach Iscol, New York City’s commissioner of emergency management, defended the city’s alerts, saying officials had to confirm with the U.S.G.S. that the shaking was in fact caused by an earthquake. The alerts were sent out in 14 languages.

By the standards of the biggest earthquakes that can cause mass devastation, Friday’s shaking was very minor. The magnitude-6.7 earthquake that struck the Northridge neighborhood of Los Angeles in 1994, causing billions of dollars in damages and killing 57 people, was more than 700 times as strong as the temblor in the northeast on Friday.

At its epicenter in New Jersey, Friday’s quake produced shaking of about V on the Mercalli Intensity Scale, an average of the intensity of shaking reported by people who felt it. The scale uses Roman numerals. Damage to buildings typically begins to occur at around VII on the scale, according to Ron Hamburger, one of the country’s leading structural engineers who specializes in seismic safety. Friday’s earthquake, he said, “would have been a nonevent in California.”

But around New York and New Jersey, the suddenness of the shaking and unfamiliarity with earthquakes left many people startled.

In Whitehouse Station, Valorie Brennan heard a rumbling that sounded like a train, before she felt any shaking.

“I thought my furnace exploded,” she said. “My dogs went running to the back of the house to hide.”

At the riding stables, in Califon, N.J., pictures of show jumping horses fell off the tack room walls and shattered, as the riders dismounted and tried to soothe their trembling horses while aftershocks rumbled beneath their hooves.

In the Marble Hill neighborhood of Manhattan, Ada Carrasco was washing dishes in her third-floor apartment when the shaking started. “I felt it, but at first, I thought to myself, Am I getting lightheaded? But then the shaking continued and I ran out the door,” she said in Spanish.

“I’ve never experienced this in my life,” said Kristina Feeley, who works behind the counter at the Oldwick General Store in New Jersey. The earthquake did not cause damage, but reverberated for 30 seconds throughout the shop. Everyone froze, Ms. Feeley said, and it was several minutes before the floor felt steady enough to move across.

Friday’s quake occurred along the Ramapo system of faults, the fractures between two blocks of rock in the Earth’s crust. The system runs through arms of the northern Appalachian Mountains in New York, New Jersey and Pennsylvania.

The magnitude of 4.8 was quite large for the fault system, according to Folarin Kolawole, a geologist at Lamont-Doherty Earth Observatory at Columbia University, which is in Palisades, N.Y.

“There’s been nothing close to this for a long time,” Dr. Kolawole said in an interview.

At Lincoln Center, the New York Philharmonic briefly delayed the start of its 11 a.m. performance because alerts were still going off on people’s phones.

At the United Nations in Manhattan, Riyad H. Mansour, a Palestinian diplomat, joked that Janti Soeripto, the president and chief executive of Save the Children U.S., was “making the ground shake” as she delivered an update to the Security Council on Gaza just as the quake struck.

While earthquakes in New York City are surprises to most, seismologists say the ground is not as stable as New Yorkers might believe. A study in 2008 found that a magnitude-5 earthquake occurs in the area roughly once a century. An even larger magnitude 7 is estimated to happen once every 3,400 years.

In the early 2000s, the city began requiring that building designers take seismic considerations into account. Before that, the major natural threat that the city’s building code covered was wind, which can exert very strong pressure on buildings, especially skyscrapers. The vast majority of the 1.1 million buildings in New York City were constructed before 2000 and thus not designed with earthquakes in mind.

Even the new requirements, though, are much less rigorous than those in California, where buildings must generally be designed for earthquakes three times as strong. The constellation of major seismic faults in the state can produce much more powerful quakes than those seen on the East Coast.

“I would describe the risk of a major earthquake disaster in New York of being very low — even given the inventory of old buildings,” said Mr. Hamburger, the structural engineer who specializes in seismic safety.

Hours after the earthquake on Friday it was business as usual. The New York Police Department’s chief of transit, Michael Kemper, said in a social media post that there were no reports of structural damage to the subway system, nor were there service disruptions as a result of the earthquake.

United Airlines said in a statement that “a few” flights had been diverted away from Newark Liberty International Airport, but that it was working to get those flights to the airport as soon as possible.

For Clara Dossetter, 23, and her father, David Dossetter, 67, the earthquake presented an opportunity. Mr. Dossetter was visiting New York from San Francisco, and they were preparing to go up the Empire State Building when the quake struck. Ms. Dossetter asked her father whether they should reconsider.

“He was like, ‘No, that’s better because no one will be there,’” she said.

Reporting from around the Northeast was contributed by Lola Fadulu, Gaya Gupta, Hurubie Meko, Michael Wilson, William J. Broad, Kenneth Chang, Emma Fitzsimmons, Sarah Maslin Nir, Erin Nolan, Mihir Zaveri, Maria Cramer, Grace Ashford, Camille Baker, Liset Cruz, Michael Paulson, Patrick McGeehan and Troy Closson.