The US National Weather Service's Pacific Tsunami Warning Centre has warned that "hazardous tsunami waves" are possible for coastal regions located within 1000km of the quake's epicenter, limiting any potential waves to the PNG and Solomon Islands region.
The 7.7 quake struck the island of New Ireland in Papua New Guinea. "However... based on all available data... there is no tsunami threat to Hawaii". It said the quake struck 10 kilometers (6 miles) below the seabed, which is very shallow.
But the Ministry of Civil Defence and Emergency Management and GNS Science said the natural disaster, which happened at 12.58am on Wednesday, New Zealand time, did not pose a tsunami threat to New Zealand.
Kokopo town has a rapidly grown population of more than 20,000.
It later said the tsunami threat had largely passed and no waves had been observed, but that there were no sea level gauges in the area for measurement.More news: How much coffee is too much? Your Questions Answered
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The Ministry of Civil Defence and Emergency Management told 1 NEWS the quake was assessed by GNS Science as having no tsunami threat to New Zealand.
There were no initial reports of serious damage but the full picture may not become clear until daylight.
"We are conducting the assessment starting this morning", he told Reuters news agency by telephone.
The warning covers the Solomon Islands and Papua New Guinea.
Earthquakes in the mountainous nation, which is on the so-called "Pacific Ring of Fire", do rarely cause damage or casualties because many structures in the region are light and flexible.