Report warns NZ not well prepared for tsunami threat

A tsunami is likely to kill many times more people in New Zealand than an earthquake, says a new report.

Damage to buildings from a giant wave could also be twice as bad, although trying to make predictions was dangerous, says the report from state-owned seismology institute GNS Science.

The report is the first attempt to comprehensively assess the threat to New Zealanders from a tsunami and was commissioned by the Government after the devastation from last year's Boxing Day tsunami in the Indian Ocean.

The report emphasised the uncertainties of trying to predict damage from tsunamis.

The potential loss of life from a 500-year event in Auckland was estimated at 122 but actually ranged between 24 and 519. For Christchurch, the figure was 280 but the range was between 60 and 1500.

With effective warning systems in place, those losses could be reduced by up to 95 per cent, the report said.

It also said more work was needed on tsunami warning systems.

Many regions did not have tsunami-specific warnings and civil defence staff needed better information if or when a warning of a distant tsunami came from Hawaii's Pacific Tsunami Warning Centre.

A distant tsunami - which could take between three and 12 hours to reach New Zealand - would be much easier to prepare for because of New Zealand's link to the Hawaii centre and because it would give people time to get to higher ground.

But New Zealand had no means of monitoring for tsunamis close to its coast with travel times of between one and three hours, the report said.

It recommended the GeoNet seismic monitoring network, operated by GNS Science to monitor earthquakes in or near New Zealand, be expanded from the 45 instruments it has now.

It also recommended harbour buoys measuring water height around the country be linked to a national database.

But public education, including signs at beaches, was probably the only practical warning system for tsunamis with travelling times of three hours or less.

Civil Defence Minister Rick Barker said the report was the most comprehensive assessment of tsunami risk to date.

"The threat is bigger than we thought but effective preparation by New Zealanders can greatly reduce the risk of death or injury," he said.

The Auckland Region Civil Defence Management Group welcomed the report.

New Zealand has had 40 tsunamis in the last 165 years.

Regions at risk
* Highest Gisborne
* Napier/Hastings
* Wellington
* Christchurch

Lowest Taranaki
* West coast of regional Auckland