SYDNEY, Aug 1, 2011 (AFP) - The Pacific island nation of Papua New Guinea was jolted by a powerful 6.8-magnitude earthquake Monday, prompting a minor tsunami warning, but there were no immediate reports of damage or injuries.
The US Geological Survey said the quake occurred at a depth of 16 kilometres (10 miles), some 131 km (81 miles) east of Wewak and 706 kilometres north of the capital Port Moresby.
"No destructive widespread tsunami threat exists based on historical earthquake and tsunami data," the Pacific Tsunami Warning Centre said.
"However, earthquakes of this size sometimes generate local tsunamis that can be destructive along coasts located within a hundred kilometers of the earthquake epicentre.
"Authorities in the region of the epicentre should be aware of this possibility and take appropriate action."
GeoScience Australia measured the quake at 6.6 and said it would have been felt more than 800 kilometres (496 miles) away, but damage would only have been caused within a radius of 67 kilometres from the epicentre.
The PNG Geophysical Observatory said that residents of the coastal town of Wewak, home to about 18,000 people, would have been severely shaken, but early reports suggested no major damage or injuries.
"Preliminary reports we are receving indicate that no real life-threatening damage and it is not an event where a tsunami is thought to be generated," spokesman Lawrence Anton told AFP.
"This zone marks the boundary between two plates and so the quake was shallow... this was at a shallow depth and not too far from Wewak so it would have been felt strongly there.
"The way the quake occured is not the same as those that can generate tsunamis -- it was more of a horizontal plate movement, not a vertical one."
Papua New Guinea, which is mired in poverty despite rich mineral deposits, sits on the so-called "Pacific Ring of Fire", a hotspot for seismic activity due to friction between tectonic plates.
A giant tsunami in 1997, caused by an undersea earthquake or a landslide, killed more than 3,500 people near Aitapi, on the country's northwest coast.