The US Geological Survey said the earthquake hit at a depth of 12.6 km on Friday, with an epicentre in a sparsely populated area about 200 km from the capital, and that some casualties were possible.
In the following hours, even as more than 40 aftershocks rattled the isthmus nation, the Panama Canal and Cobre Panama copper mine reported normal operations and the Tocumen International Airport lifted a suspension on flights.
Office workers in the upscale business hub of downtown Panama City fretted about how to get home in the snarl of traffic, after the quake sent thousands into the streets.
Juan Sanchez, a 37-year-old economy ministry employee, waited for a bus he said he doubted would arrive.
"They evacuated all of these buildings. Everyone is outside. Now the problem is, how do we get home?"
President Raul Mulino travelled to Penonome, a city about halfway between the epicentre and Panama City, where some buildings collapsed and a church was damaged.
Despite the force of Friday's tremor, the country appeared to have been spared the destruction of other recent powerful quakes in the region, with no deaths or injuries immediately reported.
Back-to-back quakes in Venezuela in June killed several thousand people, while a quake in Colombia in August killed more than 300.
An exposure report by the USGS estimated about 43,000 Panamanians lived in areas with at least severe exposure to the quake. This compares to nearly 1.4 million in the area of the twin quakes in Venezuela and over 1.6 million in the quake-hit zone of western Colombia.
Nestor Luque, director of Panama's geosciences institute, attributed the quake to the Azuero Sona Fault System that he said contained a massive buildup of pressure that was occasionally released.
"The seismic signals have travelled throughout the national territory and that is why it could be felt everywhere."
In Panama City, Luque said he counted 40 seconds of vibrations, though other areas may have felt even longer tremors.
Sabina Rios, who was on the sixth floor of an old US military-era building in Panama City, said the shaking was unusually strong and prolonged.
"The quake felt strong and lasted a long time, the longest I've felt in years," Rios said.
Strong earthquakes are not common in Panama.
Panama was due to hold a national evacuation drill on Monday to test the country's emergency response.
