The quake came a day after Chile was shaken by an 8.2 magnitude quake that killed six people and set off a tsunami with 7-foot (2-meter) waves.
The Panama quake was centered about 38 miles (61 km) south of David, Panama, at a depth of 17.3 miles (28 km). The USGS originally reported the magnitude at 6.2 and depth at 6.2 miles (10 km).
Panama's head of emergency services, Arturo Alvarado, said there were no reports of damage or injuries but that schools and homes in the area were evacuated as a precaution. A USGS tweet said it had received citizens' reports of light and moderate shaking.
(Reporting by Bill Trott; Editing by Jim Loney)