The quake struck 175 km east of Kandrian on New Britain and 577 km northeast of the capital Port Moresby.
Its epicentre, with a depth of 21.50 km, was initially determined to be at 5.9944 degrees south latitude and 151.0950 degrees east longitude.
An official at Geoscience Australia said that it was not likely to cause any damage.
Papua New Guinea, which is mired in poverty despite rich mineral deposits, sits on the so-called "Pacific Ring of Fire", a hotspot for seismic activity due to friction between tectonic plates.
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