USGS geophysicist John Bellini says Friday night's earthquake was centered near Cornwells Heights and Eddington, Pa., just northeast of Philadelphia and west-northwest of Beverly, N.J.
Bellini says the magnitude-1.7 quake was so small it was unable to do any damage. He says to residents it might have sounded like "a big truck going by."
Earthquakes are fairly common but usually are so small people don't feel them. A quake generally would have to be at least magnitude 2 or 3 to be felt. A quake of magnitude 4 can cause moderate damage.
The U.S. Geological Survey said Saturday it had no reports of anyone feeling Friday's quake. But local police and firefighters say some residents felt their houses shake.
A large number of police and fire vehicles were called to the area of Knights Road and Fairdale Road in Northeast Philadelphia Friday night.
Residents reported hearing and feeling several strong blasts shortly after 9:30pm.
Hundreds of people called 911 after the jolts, which were also felt in Lower Bucks County.
Emergency officials were unable to find evidence of an explosion.
PECO says there has been no gas explosion in the area, and there has been no sign of damage and no reports of injuries.
The U.S. geological survey initially ruled out a tremor, but confirmed the quake Saturday afternoon.
Another rumble was felt early Saturday morning on Whiting Road, not far from where the original blast were felt.
To learn more about earthquake activity in your area, visit the USGS website at http://www.usgs.gov/.
