Aftershocks expected within next week following New Jersey earthquake: USGS forecast

An aftershock following a 4.8 magnitude earthquake that rattled New Jersey, New York and Philadelphia, was felt in New York City and parts beyond, according to the U.S. Geological Survey (USGS). But this was to be expected. 

There will be almost an 80% chance of a magnitude 3 and above aftershock within the next week, the USGS predicted. And within that time, it is most likely that up to five will occur. 

"Magnitude 3 and higher aftershocks are large enough to be felt nearby. The number of aftershocks will decrease over time, but a large aftershock can temporarily increase the number of aftershocks," the USGS said. 

The latest aftershock happened at 5:59 p.m. ET just southwest of Gladstone, New Jersey, and was 3.8 in magnitude. Before that, a 2.0-magnitude aftershock was recorded near Bedminster, New Jersey, an hour after the initial quake. 


FILE - In this photo illustration, an emergency alert is displayed from the national Emergency Broadcast System warning of an earthquake in the area on April 5, 2024 in New York City.

What is an aftershock? 

Aftershocks are basically smaller earthquakes that occur in the same general area during the hours, days and years following a larger quake, or the "mainshock," according to the USGS. 

Aftershocks usually mean that the ground is readjusting itself following the main earthquake. 

Earthquake in New Jersey

The earthquake that happened in New Jersey on March 5, was 4.8 in magnitude and struck near Lebanon, though the impacts were felt in New York City, Philadelphia and in other nearby cities. 

USGS figures showed the quake could have been felt by more than 42 million people. 

Earthquakes are less common on the eastern than western edges of the U.S. because the East Coast does not lie on a boundary of tectonic plates. But 13 earthquakes of magnitude 4.5 or stronger have been recorded since 1950 within 500 km (311 miles) of Friday's tremblor, the USGS said. The strongest was a 5.8-magnitude quake in Mineral, Virginia, on Aug. 23, 2011, that jolted people from Georgia to Canada. 

The Associated Press and Heather Miller contributed to this report. This story was reported from Los Angeles.