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Tsunami in New Zealand

Has New Zealand been hit by tsunamis?

New Zealand has experienced about 10 tsunamis higher than 5m since 1840. Some were caused by distant earthquakes, but most by seafloor quakes not far off the coast.

2013 Tsunami Report

A nearby coastal seafloor earthquake is the only warning people may get before a tsunami arrives. Such a tsunami can arrive within minutes - before there is time to issue a warning. Distant earthquakes give more warning time. Some tsunamis are turbulent, foaming walls of water filled with debris and sand that crash ashore and sweep inland. Others are just rapidly rising or falling water levels over minutes to an hour. Both are dangerous. Both can travel over land at speeds faster than a person can run. The turbulent surge is invariably more destructive because of the churning and faster speed of the water.

How vulnerable is New Zealand to tsunamis?

Quite vulnerable. Tsunami hazard for the Pacific is higher than for other oceans because of the "Ring of Fire" - the zone of earthquakes associated with the tectonic plate boundary that bounds the Pacific. In New Zealand, scientists consider the tsunami hazard from two viewpoints - Pacific-wide events for which there will be some warning, and "near-source" tsunami generated by large offshore New Zealand earthquakes, landslides, and volcanic eruptions. The list of possible local tsunami sources is long. Because tsunami research is relatively young (compared to other geological hazards), the state of knowledge about the severity and frequency of local and distant tsunamis is poor. One of the main challenges facing tsunami researchers is that evidence of tsunamis does not stay in the landscape as it is eroded by natural processes. Impacts of past tsunami are therefore difficult to identify, unless someone was around and wrote about them at the time.

Does New Zealand have a tsunami warning system? If so, how does it work?

New Zealand has a warning system for tsunamis caused by distant earthquakes (such as in South America), but does not have a warning system for tsunamis caused by local events. Why? Because tsunami generated by local earthquakes can arrive at the nearest coast before scientists can calculate the location of the earthquake and issue a warning.

The only country to have a warning system for tsunamis caused by nearby earthquakes is Japan. This is because they have an automatic earthquake location system based on hundreds of seismographs, AND because Japanese scientists have estimated in advance what tsunamis could be caused by 100,000 different earthquakes at 10,000 locations around their coastline.

As far as tsunamis coming to New Zealand from distant places, the Ministry of Civil Defence and Emergency Management receives warning from the Pacific Tsunami Warning Centre in Hawaii. Ministry of Civil Defence and Emergency Management is responsible for evaluating the danger to New Zealand, and will ensure national or regional warnings are issued, if necessary. Tsunamis from South America, Alaska, and Japan, take more than 12 hours to reach New Zealand, giving authorities time to make decisions.