Tsunami video urges quick response
A new tsunami warning video is hammering home the message that people near the coast need to move fast if a big earthquake hits.
Made by GNS Science and set in Wellington it warns: "Local tsunami are generated very close to New Zealand, and could take only a few minutes to reach the coast. There will not be time for an official warning."
When the source was local, a tsunami would take less than an hour to arrive.
"In those cases, the earthquake will be your only warning," GNS Science natural hazards scientist Dr Graham Leonard said on the video.
"Because if you're really close to the fault, the tsunami could arrive within minutes, it's important to not wait for anything. Leave immediately, head to higher ground or inland and stay away for many hours." People should not return until an official all clear was given.
"Waves can keep coming for hours, or even tens of hours from a distant source."
Maps had been drawn up showing zones that needed to be evacuated around the coast in case of a tsunami.
"If you feel a large earthquake, longer than a minute, or too strong to stand up in easily, you need to evacuate all of the zones immediately. You don't know how big it's going to be, and those earthquake fault sources are close by, potentially," Leonard said.
All New Zealand's coastline was at risk from tsunami, but some areas were at risk of bigger or more frequent events.
The east coast of the North Island faced a big subduction zone fault. Tsunami from such large faults could be similar to those in Japan in 2011 and in the Indian Ocean in 2004.
In the case of the largest subduction zone tsunami, it would be necessary for people in steep areas close to the coast to get to a point beyond 35 metres above the beach.
"Head uphill or inland. Every metre you go, the safer you get."
In communities on the Wellington south coast, a blue line had been painted on roads at the level which the largest tsunami could reach.
Most tsunami were caused by earthquakes, with other causes including submarine landslides, volcanic eruptions, landslides going into the ocean, and very rarely an asteroid hitting the ocean.
Faults on the other side of the Pacific, particularly in Peru, and elsewhere around the Pacific Ring of Fire including Chile, North America and Japan could send tsunami toward New Zealand. In those cases this country would probably get 10 or more hours of warning.
Leonard told Fairfax Media that a tsunami that might be only a metre high on the open ocean could get up to 17m high at the beach in a worst case scenario. In steep areas such a wave could then reach a run-up height of double that.
The Dominion Post