The aftershock was reported just before 10:30 a.m.
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It comes just days after an earthquake with a magnitude of 4.8 startled millions of people in the East Coast on Friday morning.
The epicenter was near Whitehouse Station, New Jersey -- about 60 miles northeast of Philadelphia. It had a depth of about 3 miles, the U.S. Geological Survey said.
Throughout the course of the day, several more aftershocks were felt in the area, and experts warned aftershocks could be felt for up to a week after the primary event.
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Friday's earthquake was the largest in the region area since 1973.
An earthquake between 4.0 and 4.9 is considered to be minor to moderate. There are an estimated 13,000 earthquakes in that range worldwide every year, according to a chart from Penn State University.
The next-strongest earthquake in the Philadelphia area was 4.6 magnitude, in Sinking Spring, Berks County on Jan. 16, 1994.
Over 120,000 people reported feeling Friday's earthquake to USGS, all the way south to Delaware and north to Connecticut and upstate New York.