The observatory said the quake was located a little more than 2 miles southwest of Morris Plains just after 6:30 p.m.
Some Morris County residents posted on social media that they felt the ground shake, and some reported hearing loud booms.
Jessica Turner, a USGS geophysicist, said the tremor was noticeable because its epicenter was directly beneath Morris Plains. Morris Plains Police Lt. Michael Koroski said police received about 25 calls reporting a loud booming noise, but there were no requests for service because of the quake.
There were no reports of any damage.
The Associated Press news wire service contributed to this report.