A shallow 6.6-magnitude earthquake struck off the New Britain coast of Papua New Guinea on Thursday, the USGS said, but no tsunami warning was issued.
The US Geological Survey put the depth of the quake at just 21 kilometres (13 miles), although Geoscience Australia said it was 37 kilometres.
The quake struck 175 kilometres (109 miles) east of Kandrian on New Britain and 577 kilometres northeast of the capital Port Moresby.
"It was pretty benign," said an official at Geoscience Australia. "It is not likely to have caused 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.
A giant tsunami in 1997, caused by an undersea earthquake or a landslide, killed more than 3,500 people near Aitapi, on the country's northwest coast.