The quake was recorded approximately 230km off of Papua New Guinea at a depth of 5.7km, the United States Geological Survey said.
The island chain is part of the so-called "Ring of Fire" – a string of volcanoes around the Pacific that make it a seismically active area.
A tsunami warning has not yet been issued.
Locals reportedly felt the powerful tremors at 6.30am local time (9.30pm UK).
The Pacific Ring of Fire has sprung to life in the last week. with numerous intense quakes felt around it.
They include ones in New Zealand, Vanuatu, Japan, Indonesia and Mexico.
The Mexico quake was particularly devastating, with hundreds left dead and widespread damage in the capital.
There are also fears of a volcanic eruption on the island of Bali – also within the Ring Of Fire.
Residents living near Mount Agung have been put on the country's highest alert and forced to flee for their safety.
The 10,000ft-high volcano – which last blew more than 50 years – was spotted spewing out magma as plumes of smoke rise from the crater.
Yesterday as many as 50,000 have been evacuated, according to the Red Cross.
