The devastating quake hit at around 3:40am local time at a depth of 10 km (6 miles), the US Geographical Survey (USGS) said.
Officials at the Pacific Tsunami Warning Centre said that, based on the current evidence, there is no tsunami threat to nearby islands.
At least 55 people died in a separate earthquake in Papua New Guinea last week, although authorities fear the toll could exceed 100.
The 7.5 magnitude disaster, which took place last Monday, destroyed homes, triggered landslides and halted work at four oil and gas fields.
Southern Highlands governor William Powi yesterday people were feeling traumatised from the earthquake and ongoing aftershocks.
He said: “It is beyond the capacity of the provincial government to cope with the magnitude of destruction and devastation.
“Our people are traumatised and finding it difficult to cope.”
Australian Sally Lloyd, who is visiting Papua New Guinea, said villagers were terrified by the constant shaking.
She said: “It is terror. They think the end of the world is happening.”
The Pacific Ring of Fire is the most geologically active area in the world, with more than 90 percent of earthquakes occurring there.
The recent volatility in the region has increased fears for the Big One: a major earthquake in a highly populated area on the US west coast or in Japan.