A magnitude 7.5 earthquake struck off Bougainville in Papua New Guinea on Saturday and a tsunami warning was briefly issued for the island and neighbouring Solomon Islands.
The US Geological Survey said the quake was at a depth of 10km and centred 68km southwest of Bougainville just before 11.30pm (AEST). The agency has revised the magnitude from an initial 7.8.
A tsunami warning was briefly issued afterwards, but Civil Defence says it did not extend to New Zealand.
At least six strong quakes have occurred near Bougainville in the past two weeks, including a magnitude 7.3 on 11 April.
Earlier on Saturday, USGS reported a magnitude 6.6 tremor in the same area.
"Certainly it has been very active, more active than usual," said seismologist Jonathan Bathgate of Geoscience Australia. "(The spate of earthquakes) is relieving some pressure on this faultline, but we can't rule out another large earthquake."
In 1998, a magnitude 7.0 earthquake triggered a tsunami on the north coast of Papua New Guinea that killed more than 2000 people.
