"So it is likely that at least one such event will occur in the lifetime of most New Zealanders," Dr Power said.
In 1947 the magnitude 7.0-7.1 Poverty Bay earthquake generated one of the largest tsunamis in New Zealand's history that created tsunami run-ups in Napier.
Dr Power said it was impossible for estimates of size and frequency to be exact. But underplaying the danger would be irresponsible, as it could put people at risk.
Hawke's Bay Civil Defence emergency management group manager Ian Macdonald said local authorities are constantly updating their emergency plans in the event of a large-scale natural disaster.
"It is an ongoing process and when we get new information like this we see how it impacts on the inundation areas," Mr Macdonald said.
The inundation areas are calculated predictions for how far a tsunami wave would go inland.
The 2011 Hawke's Bay Civil Defence model is based on a 10m wave.
"The difference between a 10m and 12m wave, in terms of the inundation area, is unlikely to be significant," said Mr McDonald.
He said costal experts from the Hawke's Bay Regional Council have determined the inundation extent, allowing Civil Defence to plan for potential damage.
"We are further ahead than almost any other parts of the country with our emergency planning. Lots of areas don't have any modelling.
"We have to understand that this is a really rare event, with a 0.4 per cent chance per year of a 12m wave hitting our coast.
"However, the impacts of a 12m wave would be significant."
He said due to the potential destruction a 12m wave could inflict it is listed in the regions top two "potential hazards list".
"A tsunami is second on our list.
"An earthquake number one and volcanic ash fall number three," said Mr MacDonald.
A human pandemic and flooding round out the top five.
He said in the event of a large earthquake and subsequent tsunami there may be as little as half an hour before the wave struck, while local authorities may not be able to get a warning out.
"If there is an earthquake that you can't stand up in or lasts longer than one minute and you live in a coastal area, you need to get to higher ground."
"There are a number of fault lines off the Hawke's Bay coast that could generate a wave they [GNS] are talking about."
The GNS report said larger tsunamis were possible because there was more uncertainty about the maximum size of earthquakes on plate boundaries.
While a tsunami generated by nearby offshore ruptures represent a higher threat, distant tsunami, from across the Pacific are a smaller threat than shown in the 2005 report.
A GNS Science spokesman said Hawke's Bay, East Coast and Wairarapa would remain among the most vulnerable areas, due to the location of the plate boundary in relation to the NZ land mass. In particular, the location of the Hikurangi subduction zone.
"Scientists think this plate interface zone could be capable of producing a large sea floor quake which could send a tsunami ashore with little warning," he said.
Other areas of New Zealand where tsunami pose a greater hazard than previously understood include Northland, northwest Auckland, Great Barrier Island, the Coromandel Peninsula, and Bay of Plenty, the North Island's East Cape, the Wairarapa coast, Southland, Stewart Island, Fiordland and Westland.
