New York City Rattled by 4.8 Magnitude Earthquake and Aftershock

A 4.8 magnitude earthquake struck near Whitehouse Station, New Jersey, at 10:23 a.m. ET on Friday morning. Tremors were felt throughout the state, New York City, Philadelphia, and as far south as Baltimore. The earthquake’s epicenter was in Lebanon, N.J., a city in the North-Central part of the state.

Per the United States Geological Survey (USGS), the earthquake is one of the strongest recorded in the Northeast in over a decade. There were no immediate reports of major injuries or damage.

There have been at least 18 aftershocks, ranging in magnitude, following the morning earthquake, according to the USGS. The most notable aftershock occurred in Gladstone, New Jersey, just before 6 p.m. on Friday and initially had a registered magnitude of 4.0, before being adjusted to 3.8. This came after Alexandra Hatem of the (USGS) warned TIME there was around a 45% chance of an aftershock of magnitude greater than 3.0 occurring within the next week.

On Saturday morning, ABC7 New York reported two further aftershocks—of 2.5 and 1.9 magnitude—had taken place since 6 a.m. local time, noting that people had reported feeling the 2.5 magnitude aftershock.

Speaking during a media briefing on Friday afternoon, Sarah McBride of USGS remarked that the morning earthquake was so widely felt, it may have set a record. “This earthquake was widely felt and we know this because we have received more than 160,000 ‘Felt Reports’ on our website.” If you felt the earthquake, you can report it to the USGS here. This helps scientists gather more information about the shaking caused by earthquakes around the world.

At a press conference on Friday, Governor of New York Kathy Hochul said that Newark Liberty International Airport in New Jersey and John F. Kennedy International Airport had undergone full ground stops in the aftermath of the earthquake while the potential for aftershocks was being assessed. Flights resumed thereafter.

Hochul urged New Yorkers to take precautionary measures in case of an aftershock. “Drop to the floor, cover your neck, and hold on to something that is sturdy,” she advised. “If you hear any shifting or any unusual noises, leave your home and go outside. You're safer there than in a building that could be crumbling around you.”

Hochul also encouraged residents to check their homes for damage, including gas and water lines. An overloading of cell service was reported immediately in the aftermath of the main event, but networks then resumed normal service.

“These are emerging situations. It could be over, but also there could be another effect. We have to be prepared for that and warn New Yorkers to be particularly vigilant in the days following an earthquake,” said Hochul on Friday.

Are earthquakes becoming more frequent? 

Seismologist Angie Lux of the Berkeley Seismological Laboratory tells TIME that the current level of seismic activity is consistent with what would be expected in the region. “Looking at the sort of historical seismicity in the area, I would definitely say that there's no clear trend of more earthquakes that are happening.”

A 5.8 magnitude earthquake occurred on the East Coast in August 2011. It struck Virginia, and was felt as far as Boston.

While earthquakes are not as common in the Northeast as they are on the West Coast, earthquakes east of the Rocky Mountains can often cause shaking at much further distances than earthquakes of a similar magnitude on the West Coast. This is thought to be because rocks on the West Coast are younger and more broken up than rocks found along the East Coast, which means that they are able to absorb more of an earthquake’s seismic energy, according to an article published by the USGS.

Lux says that large earthquakes are capable of happening anywhere across the mainland U.S. “The potential for really significant earthquakes is lower [on the East Coast] than we see in other places, but there's always a possibility of earthquakes if we look at the seismic hazard maps,” says Lux.

Human activity can also impact the frequency of earthquakes. Practices like fracking and drilling have been shown to increase the seismic activity in places like Oklahoma and Texas.

Nevertheless, the Northeast remains vulnerable since unlike California and other Western states, building codes in the East Coast are not designed with major earthquakes in mind and earthquake early warning alert systems are not in place.

Reactions to the earthquake from New York and New Jersey

TIME employees across New York City and New Jersey shared their experiences of the earthquake on Friday morning.

“I live on the first floor of an old building in Flatbush, Brooklyn, and I truly thought that something was about to explode in the basement,” says Erin, who was working from home when the earthquake struck.

Meanwhile Chardia, who lives on the 23rd floor of a building in the Bronx, says she was on a virtual call with her team when the earthquake hit. “We all live in different parts of New York, and you could see the confusion across each face as the screens began to shake and the ‘Did y’all feel that’ messages came rushing through,” she says. “It's a surreal feeling of helplessness.”

In downtown Manhattan, Melody noticed the earthquake when she saw colleagues shaking on her computer screen during a weekly video call. “I thought my dog was stuck under the couch trying to rattle out or something because my couch and the floor moved,” she says. “I realized it was an earthquake and got worried she would be smooshed under the couch, but then I see[n] her calm as ever laying in her doggy bed, staring at me.”

California-raised Melody says that she remembered earthquake drills from her upbringing, telling her to stay inside, away from windows, and seek cover under hard objects. “Drop, cover and hold onto something,” she adds. 

Tameka—who lives in South Jersey—says her dog reacted before her, by running into her workspace area “seeming frantic and worried.” She says that “by the time I could respond to her, the shaking started. It was over before we made it to the nearest doorway in my apartment.”

Recent news coverage of the earthquake in Taiwan left Tameka feeling “mildly prepared” for Friday’s events. “Without such timely news of another earthquake, one hitting here would've been the farthest from my mind," she notes.