The USGS said the quake was 51 kilometres (31.6 miles) deep and located 123.2 kilometres from the closest town of Kokopo.
The Papua New Guinea National Disaster Centre said it was assessing for damage.
A hotel receptionist in Kokopo, Vernon Gash, told AFP the earthquake was "a bit intense" and lasted under a minute.
"We are used to it, it happens all the time," he said, adding there was no damage to the hotel.
There were no tsunami warnings issued following the earthquake.
Earthquakes are common in Papua New Guinea, which sits on top of the seismic "Ring of Fire" -- an arc of intense tectonic activity that stretches through Southeast Asia and across the Pacific basin.
Although they seldom cause widespread damage in sparsely populated areas, they can trigger destructive landslides.
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