Feel that? Aftershocks are still hitting N.J. nearly 5 months after large earthquake

Over the last few months in New Jersey, you may or may not have felt the earth continuing to shake beneath your feet. And that may be a continuing trend for at least the next couple of months, if not a bit longer.

Those quivers you've felt (or not felt) are aftershocks, and there have been more than 200 of them since a major 4.8 magnitude earthquake in early April centered in Tewksbury in Hunterdon County rocked the eastern United States.

Dr. Thomas L. Pratt, a research geophysicist for the U.S. Geological Survey, said that while an earthquake of that magnitude is unusual for the Garden State, the number of aftershocks the area has experienced is not.

"When earthquakes like that do happen, there are often lots of aftershocks and this one has caused a great deal of them," Pratt told NJ Advance Media. "It's not uncommon for there to be hundreds of aftershocks and they can go on for many months, even years."

"The bigger the earthquake, the longer the aftershock experience," he added.

He said he suspects they will continue into 2025, but added they tend to get lower in intensity.

For example, since the start of September, there have been six aftershocks with the largest being a 1.9 on Sept. 9 centered about 7 kilometers east of Califon, another municipality in Hunterdon County.

The most recent, a 1.6 magnitude earthquake, happened on Monday at 5:11 a.m. Monday about two kilometers west of Gladstone in Somerset County.

Four people reported experiencing weak shaking and one felt light, slightly stronger shaking in the area, but no damage was reported, according to U.S. Geological Survey data.

Pratt said people don't usually feel quakes that are lower than 1.5 magnitude and that researchers usually can't detect ones that are around 1.1 or 1.2.

He added that the closer a person is to a earthquake, the more the person will feel it.

Also, there is a chance, albeit a small one, that April's earthquake could be a precursor to an even larger one, Pratt said.

"We can't eliminate the possibility that these are leading up a bigger earthquake, but it's extremely rare," he said.

Nearly all earthquakes occur on faults, features in the Earth where rocks move past each other, and Pratt said there a lot of faults in New Jersey but that most of them haven't moved hundreds of millions of years.

"The Ramapo Fault in that area, that's been a pretty major one," he said. "There's been a debate to how active it is and how much of a danger it is. (The April earthquake) was pretty close to it but not on it."

While the earthquake and subsequent aftershocks have not caused any major damage in New Jersey, Pratt said it's always good to prepared in the event of another of similar or larger intensity.

"Call it a reminder that natural disasters can happen and that you should always be prepared," he said.

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