Northland's east coast would bear the brunt of a New Zealand tsunami and lacks adequate warning systems for tsunamis, earthquakes or volcanoes, scientists say.
The region has already been hit by a major tsunami - it was estimated to be about 30m high and struck the area about 600 years ago, according to Northland's Civil Defence Emergency Management Group Plan.
And in December 2003, five earthquakes - centred about 65km south of Whangarei near Paparoa - hit the region.
The earthquakes caused little damage but shocked Northlanders who are virtual strangers to seismic activity - there have only been four bouts of earthquake activity of 4.0 or more on the Richter scale since the early 1900s.
However, in the short term experts say there's no reason to panic. It could be 500 to 1000 years before another major geological disaster affects Northland.
New Zealand is short of about 10 seismograph stations which would give the country better warning of an approaching tsunami. GeoNet, the national monitoring system, has gone from just four stations in 2001 to 36 now - a vast improvement, say scientists.
But the network still has holes in its coverage of Whangarei to the Bay of Islands, Auckland City, the Bay of Plenty, Taranaki, Marlborough, the East Coast of the North Island and the West Coast of the South Island.
GeoNet director Hugh Cowan said Northland had two recognised active volcano zones - around Whangarei and in the Bay of Islands around Ngawha - while the region's east coast, particularly, was always at risk of a tsunami.
The biggest tsunami risk came from a possible underwater earthquake or volcano off the East Cape or from South America.
"It is not among the highest hazards in New Zealand but is regarded as a centre that could bear closer monitoring in case there was any (geological) activity," Mr Cowan said.
He said while the GeoNet system was inadequate it would not miss the kind of earthquake which triggered the Boxing Day tsunami across Asia. GeoNet monitors seismic activity that could lead to local tsunamis.
GeoNet volcanologist Brad Scott said the last volcanic eruption in or around Northland was believed to have been about 10,000 years ago.
"We can't discount the possibility of something happening up there again, but it could be 500 or a 1000 years away," Mr Scott said.
He said Northland was at an even lower risk level of experiencing a major earthquake, with the region having a less than five percent chance of one occurring in the next 500 years. "Northland does have exposure to the risk of geological hazards, but by comparison to the rest of New Zealand it's a very low risk," Mr Scott said.
The Pacific Tsunami Warning Centre in Hawaii monitors activity outside the range of GeoNet's network. For tsunamis off the coast of South America, it can provide 12 to 14 hours' warning. Both networks have direct communication lines to the Civil Defence Ministry. If a warning or evacuation is necessary, national officers inform local civil defence organisations, emergency services and councils.
Northern Advocate
