Earthquake Rattles Northeast, but Little Damage Is Reported (2024)

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Here’s the latest on the earthquake.

The earthquake was not a rarity for the New York area — numerous small temblors go unnoticed every year, geologists say — but its strength and intensity unsettled a region more accustomed to flooded roadways and snow-covered sidewalks than trembling walls.

Several minor aftershocks were reported in New Jersey in the hours afterward, including one with a magnitude of 2.2 that struck at 1:32 p.m. near the original quake’s epicenter, according to the U.S.G.S.

The New York Police Department said it had no immediate reports of damage. Several East Coast airports issued ground stops halting air traffic in the immediate aftermath, but flights later resumed as normal.

Mayor Eric Adams said in a statement Friday morning that New York City did not have any reports of “major impacts or injuries,” and that the city would continue its inspections of critical infrastructure.

Later, in a news conference, Mr. Adams urged New Yorkers to be on alert for aftershocks but should otherwise proceed with their activities. “New Yorkers should go about their normal day,” Mr. Adams said.

The White House said that President Biden spoke with Gov. Phil Murphy of New Jersey and told him that his administration was in touch with state and local officials and would provide assistance, if needed.

Here’s what else to know:

• The New York Police Department’s chief of transit said on X that no structural damage had been reported within the subway system and there were no service disruptions as a result of the earthquake.

• New York City’s schools chancellor said at the news conference with Mr. Adams that all students in public schools were safe, and parents should not pick up their children early.

• New York State officials in Albany said that 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.”

• Mr. Murphy said on X that the state had activated its emergency operations center, and urged residents not to call 911 unless they were having an actual emergency. Gov. Josh Shapiro of Pennsylvania said on X that his team and the state’s emergency management agency were monitoring the situation.

• New York City officials were slow to inform residents about the earthquake. A beeping text alert went out to some New Yorkers at 11:02 a.m., nearly 40 minutes after the earthquake hit. Mr. Adams has received criticism in the past over his delayed response to emergencies, including floods and wildfire smoke.

• New York City added earthquake safety provisions to its building code in 1995, but most of the city’s roughly 1 million buildings were built before then. The city has more than 100,000 multifamily buildings made out of unreinforced brick, mostly built before the 1930s. These buildings have a higher risk of collapsing during a strong earthquake, according to the city.

• While most earthquakes in the Northeast go undetected, New Yorkers have felt several over the years. A 2.2 magnitude earthquake rattled parts of New York and New Jersey in May of last year, and a 3.6 magnitude earthquake rocked the town of Adams Center, N.Y., the month before that. In 2011, a 5.8 magnitude earthquake in Virginia led to the evacuation of City Hall and Midtown office buildings in Manhattan.

Emma Fitzsimmons, Sarah Maslin Nir, Erin Nolan, Mihir Zaveri Maria Cramer, Grace Ashford and Troy Closson contributed reporting.

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How an earthquake can throw the body and brain off-balance.

There is very little research into these phenomena, and most of it has been done in the wake of earthquakes far larger than the one that jolted the Northeast on Friday.

In Tokyo, where aftershocks are more common than in other parts of Japan, one team found that some people still experienced balance issues for as long as four months after a big quake.

“We see it with patients who get off cruises too, or get off a boat. They’ll be lightheaded or have a sensation of movement for days or even months,” said Dr. Landon Duyka, an ear, nose and throat surgeon at Northwestern Medicine.

If you are dizzy or feel like the ground is still moving after an earthquake ends, experts recommend treating it as you would other forms of motion sickness. Try looking at a spot far away and focusing on it, Dr. Duyka said, which “can often help what we call the vestibular system — or your balance system — settle down.”

If your dizzy spell doesn’t go away on its own within a few hours, or if it is particularly intense, you may want to look into over-the-counter antihistamines, like Dramamine, Dr. Duyka said.

Some feelings may be caused more by stress. Experts said that it’s normal to feel anxiety, especially if you’ve never experienced an earthquake before.

You can’t control earthquakes, said Susan Albers, a clinical psychologist at the Cleveland Clinic who has worked with patients who have weather-related fears. “That’s where it really taps into people’s anxiety, and particularly if you’re somebody who already has issues with control.”

Dr. Albers said it’s important to avoid “doom-scrolling” after experiencing a stressful event like an earthquake. If you feel compelled to read about it, she recommended focusing on scientific explanations of earthquakes and how they work, rather than the destruction they cause. This is especially helpful for children, Dr. Albers added.

She also recommended sharing your experience with people around you, talking about where you were and what it felt like. Seek out people who project a sense of ease about the event, Dr. Albers said — or, if you are able, become that person for others.

“Being around people who are calm about the situation can be really helpful,” she said. “Calm is contagious.”

Should you stand in a doorway during an earthquake? (Probably not.)

“Do not get in a doorway,” the site warns, “as this does not provide protection from falling or flying objects and you likely will not be able to remain standing.”

Keith Porter, a research professor in the Department of Civil Environmental and Architectural Engineering at the University of Colorado Boulder, said the best advice from experts is to drop, cover and hold on (to the table or whatever other furniture you take shelter under).

Seeking shelter in a doorway is risky in several ways, Professor Porter said. For one thing, many doorways have doors that swing, which can be dangerous in an earthquake. And simply walking to a doorway could expose a person to falling or flying objects.

“I would say that is outdated advice,” he said of the mayor’s doorway suggestion.

Zach Iscol, the city’s emergency management commissioner, said in an interview on Friday that he tried to emphasize that getting low under a heavy piece of furniture should be the first option.

“If that’s not available, you should try to get in the doorway,” he said.

Asked about concerns over the safety of doorways, especially in different types of buildings, Mr. Iscol said he would look into the issue to determine whether the advice the mayor provided verbally and in a statement on Friday should be updated.

The goal, he said, is to get away from things that could fall on you, whether you are inside or outside. He said that getting low under a heavy table or desk is ideal.

Robert-Michael de Groot, a coordinator at the federal U.S. Geological Survey who specializes in earthquake safety, said there was a time when doorways were more structurally stable and stronger than other parts of a house, but “that really isn’t the case anymore.”

“You can get injured if you’re moving while shaking is occurring,” he said. “So staying in your place, dropping, is actually the most important part. Getting low to the ground and sort of being able to stabilize yourself, but then finding something to protect yourself.”

The geological survey’s advice on how to protect yourself in an earthquake is clear: “If you are INDOORS — STAY THERE! Get under a desk or table and hang on to it or move into a hallway or against an inside wall.”

The survey’s website includes a link with advice from the Earthquake Country Alliance, a California group dedicated to improving earthquake preparedness.

“In modern homes, doorways are no stronger than any other part of the house,” the alliance says. “Doorways do not protect you from the most likely source of injury — falling or flying objects. You also may not be able to brace yourself in the door during strong shaking. You are safer under a table.”

Ed Shanahan and Camille Baker contributed reporting.

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An earthquake rattles New York and New Jersey, but does little damage.

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.

Across the Northeast, startled residents wondered what the shaking was.

Some ran out of their homes. Others hung on to a piece of furniture for dear life.

Then they checked in with friends and relatives, temporarily overloading some telephone services.

Lauren Hinkson felt the earthquake in Washington, Conn., about 130 miles northeast of the epicenter.

She was working from home at her kitchen table when the house began shaking and she heard a loud noise — her boiler clanging. A picture fell off the wall.

Worried that the boiler was about to explode, she ran outside and called a neighbor down the block, who said she had felt the shaking, too. That is when Ms. Hinkson realized she had just been through an earthquake.

“I had an intense response,” she said. “I couldn’t hold my phone, I was shaking so hard.” She was relieved about 25 minutes later when her children’s school sent an email confirming that all the students were fine.

In Smithfield, R.I., west of Providence, Kimberly Kowal Arcand felt the earthquake as a vibration, akin to a large truck passing nearby, she said.

Closer to the epicenter, in Bethlehem, Pa., Brittany Roberts, the manager of Grandpa Joe’s Candy Shop, noticed that glass bottles of soda began rattling on the shelves, and then the sandwich-board signs outside fell to the pavement.

“It felt like an entire semi ran over the building,” she said. “It was really scary, and I’m from California, so I ran outside.”

Abby Mahone, the director of Moravian Academy, a private school in eastern Pennsylvania, said that all three of its campuses, in Allentown, Bethlehem and Easton, felt the earthquake. Even so, she said, the mood was lighthearted: “Some teachers and students didn’t know, at first, is the building shaking because the students are having so much fun?”

In Philadelphia, though, it was business as usual at Sonny’s Famous Steaks, a cheese steak restaurant on Market Street.

“We’re surprised,” said Julisa Puma, a cashier at Sonny’s. “We heard from people in South Philly that there was an earthquake, but we didn’t feel it at all.”

Even so, the city’s 911 system was flooded with calls, according to Joe Grace, a spokesman for Mayor Cherelle L. Parker. Police officials asked residents not to dial 911 unless they had an emergency or their property or vehicles were damaged.

On the campus of the University of Pennsylvania, students said the quake shook their rooms and left pictures askew on their walls. Ron Ozio, a university spokesman, said officials had checked the campus, building by building, for damage or injuries but had found none.

In the event of aftershocks, officials warned in a campus alert: “Stay where you are and Drop, Cover, and Hold On. Get under and hold on to sturdy furniture. Protect your head and neck with arms or pillows.”

And, also, they warned, stay out of elevators.

Dana Goldstein, Mattathias Schwartz and Meredith Cummings contributed reporting.

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Here’s the forecast for aftershocks.

Earlier aftershocks were around magnitude 2.0, barely perceptible even to people standing right at the epicenter.

Larger aftershocks are also possible.

The U.S.G.S. forecasts a 45 percent chance of an aftershock of magnitude-3 or larger in the next week. The odds rise to 66 percent over the next year.

Is this a precursor to a devastating quake? Maybe, but unlikely.

Major earthquakes of magnitude-7 or higher are often preceded by modest foreshocks. But so far, seismologists have not identified any distinguishing characteristics of a given quake that would warn of an impending larger quake.

If a devastating quake occurs next week, seismologists will retroactively call Friday’s shaking a foreshock. But they have no way to confidently predict a large quake ahead of time.

Seismologists also know that large earthquakes in this part of the world are rare. A study by scientists at Lamont-Doherty Earth Observatory at Columbia University in 2008 found that a magnitude-5 earthquake occurs in the New York City region about once a century, a magnitude-6 or larger about once every 670 years and a magnitude-7 at once every 3,400 years.

That is reflected in the geological survey’s aftershock forecast, which currently says that there is less than a 1 percent chance that Friday’s quake will be followed by a magnitude-6 quake or larger. Even the chance of a comparable earthquake of magnitude 5 is only 3 percent over the next week and 8 percent over the next year.

The forecast will be updated as instruments measure new seismic data.

John Keefe contributed reporting.

Scientists expressed doubts about linking Friday’s earthquake to the coming solar eclipse.

One theory is that this may introduce additional stress along Earth’s fault lines.

“We do know that the relative position of the Earth and the moon and the sun does exert tidal forces,” said William Frank, a geophysicist at the Massachusetts Institute of Technology. “And we know that changes the stress that can be on a fault that can host an earthquake.”

But the results of several studies of the relationship between earthquakes and tides are inconclusive, according to Seth Stein, a geophysicist at Northwestern University. “If there’s any effect, it would be incredibly weak,” he said.

Earthquakes are driven most often by the motion between two tectonic plates making up Earth’s crust — either when two plates slide along each other in opposite directions, or when one slides under the other.

Both types of movements introduce strain at the junction, which often gets relieved by an earthquake.

But at the moment, it’s difficult to say that plate motion was responsible for the quake that shook the Northeast Friday morning.

“It’s not quite as obvious, because there is no tectonic plate boundary that is active,” Dr. Frank said.

Still, he added, fault lines from past activity are everywhere on Earth’s crust.

“Some of these faults can still be storing stress and be closure to failure,” he said. “And it can just require a little bit more to push it over the edge.”

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How much damage might a big earthquake do to N.Y.C. buildings?

Such masonry cannot bend or flex during an earthquake and would instead break or crumble. A strong earthquake could cause some buildings of this type to collapse.

Although earthquakes are not as common around New York City as they are in California, New York officials consider the risk they present to be high because of the city’s density and older building stock.

Most of the city’s buildings were built before 1995, when earthquake-safety provisions were added to the local building code.

An earthquake could lead to other kinds of damage, like flooding. To deal with that, city guidelines recommend that buildings in coastal areas have a base that lets water pass through, a first floor on piers, for example.

But because much of the city’s waterfront sits atop wetlands or wastelands that are somewhat unstable, an earthquake could damage a building’s foundation, making it “uninhabitable or unusable,” according to the hazard plan.

The worst earthquake to hit New York City occurred in 1884. Its estimated magnitude of 5.4 and its epicenter was between Brooklyn and Sandy Hook, N.J.

If an equivalent earthquake were to strike now, it could cause more than $4.7 billion in damage to buildings and other infrastructure, according to a city model.

Any earthquake could “compromise infrastructure such as bridges, tunnels, utility systems, dams, and highways” according to the city’s hazard plan, which acknowledges that the “seismic vulnerability of the city’s complex network of interlinked infrastructure remains poorly understood and exists as an area of high concern."

The plan also notes that “some of New York City’s critical infrastructure systems are vulnerable because they have aged and have maintenance problems.”

James Oddo, the city’s buildings commissioner, said at a news conference on Friday that the department was concerned about “downstream possibilities” resulting from the earthquake on Friday that may emerge in the coming days or weeks, including cracks in buildings or problems with retaining walls.

“If you see something that is problematic, please call 311,” he said.

New Yorkers are used to all kinds of rumblings, but not earthquakes.

In Whitehouse Station, N.J., just a few miles from the earthquake’s epicenter in Lebanon, Valorie Brennan heard a rumbling that sounded like a train, before she felt any shaking.

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

Frantic phone calls, a torrent of social media posts and an official emergency alert confirmed that the vibrating was, indeed, a magnitude-4.8 earthquake.

For many in the area, where significant quakes are uncommon, it was the first they recalled experiencing.

Ada Carrasco has lived in Marble Hill, in the Bronx, for 10 years and said she had never felt an earthquake.

She was in her third-floor apartment, washing dishes when it happened. “I felt it but at first, I thought to myself ‘Am I getting light-headed?’” she said in Spanish on the stoop of her apartment building. “Then the shaking continued and I ran out the door.”

It was also a first for Julia Gottlieb, 26, who lives in Crown Heights, in Brooklyn. She was working from home and guessed the tremor was caused by construction outside her building.

“Maybe that they were drilling too close,” she said.

But in a city teeming with transplants and tourists, some said they knew immediately what the quiver was.

Noga Hurwitz, who moved from the San Francisco Bay Area to New York for college in 2019, said she was working from her girlfriend’s apartment in Manhattan when she first felt the shaking.

Years of earthquake preparedness training from kindergarten and from her father, a geologist for the United States Geological Survey, kicked in, she said. They stood in a bedroom doorway, as she had been taught as a child (a practice that experts generally don’t advise anymore).

“It felt very intuitive,” she said, recalling the rattling picture frames and getting stuck on a roller coaster in Disneyland during some of the earthquakes she experienced growing up.

In a city whose rumbles, belches and roars normally don’t set off much alarm, she said her co-workers and friends all initially guessed that the tremor was nothing out of the ordinary in New York: something falling off an apartment building; the washing machine that rattles their apartment; roadside construction.

“There’s so many noises in New York, that I think no one’s intuition was that it’s an earthquake,” she said.

Grace Rhee, 39, was riding the Long Island Railroad with her 14-month-old son, Victor, when shaking began. Ms. Rhee, who lives in Los Angeles and works for a tech company, is in New York City visiting family.

“It’s ironic that I came here and felt an earthquake,” she said.

Was she nervous to board the subway after the minor quake? Hardly. “I’m from California. That’s nothing more than a sneeze out there.”

And before long, the city had returned to its raucous self.

Mike Irizarry, 56, a retired hair stylist who was on the subway during the earthquake and said he felt nothing, was not hesitant to get back on the train afterward.

“Look, after 9/11 and everything else,” he said, “That doesn’t scare me.”

Erin Nolan, Camille Baker and Liset Cruz contributed reporting.

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Why did New York City’s earthquake alert take 26 minutes?

By the time the alert went out at 10:49 a.m. to the more than 1 million New Yorkers who had signed up for the Notify N.Y.C. service, word of the earthquake had already spread on social media. A Wireless Emergency Alert was sent more broadly even later, with many New Yorkers reporting receiving it after 11 a.m., about 40 minutes after the earthquake had hit.

The response by the administration of Mayor Eric Adams comes after criticism over his handling of past emergencies. During major flooding and an onslaught of wildfire smoke last year, Mr. Adams was denounced for not giving residents adequate warning.

Zach Iscol, the city’s emergency management commissioner, defended the administration’s response at a news conference on Friday, arguing that officials needed time to confirm that the shaking was an earthquake and to put out the proper guidance before sending the alert.

“Twenty minutes is very, very fast for a public notification,” Mr. Iscol said.

Some elected officials were not impressed.

Shaun Abreu, a city councilman who represents northern Manhattan, wrote on social media that he didn’t know if he was “startled more by the earthquake” or the alert that was 39 minutes late. Justin Brannan, a city councilman who represents southern Brooklyn, posted the alert and wrote sarcastically, “Yes boo we know.”

When the earthquake hit at 10:23 a.m., many New Yorkers turned to X, formerly known as Twitter, for news. A series of alerts went out over the next hour, sending a cascade of beeps throughout the city.

In an interview Friday afternoon, Mr. Iscol said it was not the city’s job to “break news” to New Yorkers that the earthquake had occurred.

“The work we’re doing is to determine what is the most important guidance we need to put out in terms of life safety hazards,” he said, adding that residents might need to know about building collapses or gas leaks after an earthquake.

He said that the United States Geological Survey had confirmed the earthquake at 10:34 a.m., and the city’s alert had gone out less than 15 minutes later.

The alert at 10:49 a.m. was sent via the city’s Notify NYC electronic alert system, which has more than 1 million subscribers. The Wireless Emergency Alert was sent later to a broader number of cellphones in the New York area.

The first alert urged residents to stay indoors and to call 911 to report any injuries. A later NotifyNYC alert at 11:53 a.m. said New Yorkers could go back to their “usual activities.”

The mayor’s chief spokesman, Fabien Levy, was faster than the alert system, posting about the earthquake on social media at 10:42 a.m.

Mr. Adams, a Democrat in his third year in office, acknowledged that earthquakes were unusual in New York City and could be “extremely traumatic” for some. He urged New Yorkers to be aware that aftershocks could happen, though Mr. Iscol said the probability was “low.”

Mr. Iscol insisted that the city moved quickly enough to alert New Yorkers about the earthquake, despite a flood of complaints, including on social media.

“I think our team did a remarkable job today in getting it out to the public,” he said.

Jeffery C. Mays and Nate Schweber contributed reporting.

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Near the epicenter, the earthquake rattled plates and nerves.

“The trees, the cars, the ground,” she said about an hour later. “Fifteen minutes after, I was still shaken up — I am still shook up.”

The people here did not know it yet, but the area — in the center of Hunterdon County, about 50 miles west of New York City and 60 miles north of Philadelphia — was the epicenter of the earthquake, according to the United States Geological Survey.

Some drivers said they were on the road and initially thought they were having car trouble; others said it felt like a bomb. At the diner, about an hour after the event, Terry DeRossett said he was at home in nearby Flemington, where the glass panes of his doors shook so hard he thought they would shatter.

“The house sounded like I was inside a drum,” he said. “It was like that feeling you get from a thunderclap, but it just kept going.”

At the Oldwick General Store in Oldwick, N.J., the quake was so loud that Kristina Feeley and her colleagues initially thought a truck had crashed into the building. Everyone froze, Ms. Feeley said, and it was several minutes before the floor felt steady enough to move across it.

“Everybody — customers too — are shaken up, getting up from their tables like, ‘Whoa, this is what it feels like to walk again.’”

The quake rattled the heart of the state’s horse country, an area where farm roads are lined with fields and stables.

Mane Stream, a therapeutic riding stable, is about 100 yards from where seismologists estimated the quake’s epicenter was. Trish Hegeman, the executive director, said she knew what was happening immediately, having lived in California for nearly a decade.

She ran to a door frame and braced herself for safety in the barn office. Minutes later she headed to the barn to check on the facility’s 13 therapy horses. All were calm.

“I think one whinnied,” she said. “Amazing, given that we are right at the center.”

At a riding stables in nearby Califon, the earthquake shook the indoor arena, causing an enormous booming sound that sent the three horses galloping around the ring, heedless of their riders’ efforts to stop them. As the shaking settled, the riders dismounted and tried to soothe their trembling horses.

Dr. Brendan Furlong, an equine veterinarian whose practice is nearby, said he was about to start a procedure on a horse under sedation in a concrete barn in Lebanon Township when the barn started to rattle, items fell off shelves and the building started to squeak. The horse was jolted awake from the sedation, Dr. Furlong said.

“This poor horse,” he said, “he wanted to go somewhere.”

No one, including the horse, was injured.