A powerful magnitude 8 earthquake hit the Papua New Guinea and Solomon Islands, but no tsunami was reported hours after the Pacific Tsunami Warning Centre issued an alert for nearby islands.
The quake struck on Sunday at a depth of 103 miles under Papua New Guinea's most eastern province of Bougainville.
It was where the two South Pacific countries meet in a continuous archipelago, said Chris McKee, assistant director of Papua New Guinea Geophysical Observatory in Port Moresby.
There were no immediate reports of casualties or damage.
The greatest tsunami threat had been to Bougainville and that threat had passed without any report of a tsunami, Mr McKee said.
"I suspect that because of the great depth of the earthquake, there was probably no significant tsunami," he said.
Solomons government official George Herming said he was not aware of any major tremors being felt in his country or any tsunami.
The countries are located in the Pacific's geologically active "Ring of Fire".