Residents in several populated coastal areas of New Zealand are being warned they could be at risk from tsunamis more than 12 metres high.
New data revealed today shows the danger posed by a big wave in some centres has been underestimated and official evacuation zones will have to be widened.
The small Wairarapa settlement of Lake Ferry is in one of several coastal areas exposed to a greater tsunami risk than previously thought.
Candice Tipoki’s family has lived in Lake Ferry for 160 years and they are well prepared for a tsunami.
“As long as we have the warning systems in place and as long as we follow the guidelines and procedures that we’ve been given, I think everyone should be safe and be able to get out,” Ms Tipoki said.
The new GNS Science research will force some local councils and civil defence authorities to review their evacuation zones.
“Some of the earthquake sources around New Zealand, especially locally, can produce earthquakes that are a bit bigger and that means the waves arriving in some places can be a bit bigger,” Graham Leonard from GNS Science said.
This is because there is now more uncertainty about the maximum size of earthquakes on plate boundaries, meaning some local and regional tsunamis could be larger than previously estimated.
No New Zealand coastal area is immune from tsunamis but areas that have had the maximum wave height significantly increased include Northland; Great Barrier Island; the East Cape; Wairarapa; Auckland’s Manukau Harbour; the Coromandel (4-10m) and Bay of Plenty in the North Island. And Southland; Fiordland; Westland and Stewart Island all have greater risk in the South.
The findings come from a 220 page GNS Science report commissioned by the Ministry for Civil Defence and Emergency Management which updates a 2005 report. A tsunami generated by nearby offshore ruptures now represents a higher threat while distant tsunami from across the Pacific are a smaller threat than shown in 2005.
The report includes information gathered on the 2004 Indian Ocean, 2009 South Pacific and 2011 Tohoku tsunamis. All were produced by quakes that were substantially larger than had been considered likely at those locations.
In Auckland and Christchurch authorities are using the new data to review evacuation zones but Wellington is up to date.
“Every 10 years you could expect somewhere in New Zealand to be hit by a tsunami that’s about a metre. But history shows that every 40 or 50 years there is what we would term a ‘dangerous tsunami’,” the director of Civil Defence emergency management John Hamilton said.
Report compiler William Power, of GNS Science, said it was impossible for estimates of size and frequency to be exact but he said underplaying the danger would be irresponsible, as it could put people at risk.
“It is likely that at least one such event will occur in the lifetime of most New Zealanders,” he said.
In the capital, scientists say an earthquake from a nearby faultline could leave residents as little as 10 minutes to evacuate if it triggered a tsunami but some waves will take up to 18 hours to hit if the earthquake is in a country like Chile or Japan.
The report has not upgraded the chances of a tsunami and authorities are now developing a national smart phone app that will help residents evacuate if a wall of water does hit.
The report, Review of Tsunami Hazard in New Zealand (2013 Update), is available onthe Ministry of Civil Defence and Emergency Management website.
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