Below is more information on the different types of tsunami and what you should know and do.
If you live near the coast, think about possible evacuation routes for local, regional and distant source tsunamis. Practice these with your family or friends, and write them on your Household Emergency Plan. Find out if there are vulnerable people nearby who may need your help.
The best route to take will depend on where you are and the type of tsunami. If it is a distant source tsunami, where there is time for official warnings to be given, evacuation routes for Christchurch are given in the Evacuation information for coastal Christchurch brochure (pdf 985 kB). Evacuation routes for beach settlements in Waimakariri and Hurunui Districts are the main roads out of the settlements.
If you feel strong ground shaking and need to evacuate quickly, you may use the same route as for a distant source tsunami, or you may need to determine a faster route inland, to higher ground, or an upper storey of a building. It is your responsibility to work out the best route for you and those with you if you feel strong ground shaking or long moderate ground shaking.
If a tsunami happens in the Kaikoura Canyon, just south of Kaikoura, it would affect the coastline immediately south of Kaikoura (South Bay, Goose Bay and Oaro), but it would be too small by the time it got to Pegasus Bay to do any damage. This is because this tsunami comes from one point (an undersea landslide), rather than an offshore earthquake fault line, so the waves created decrease very quickly from the source.
The September 2010, February 2011 and June 2011 earthquakes did not cause tsunamis because they happened on land and did not displace the sea floor. The December 2011 earthquakes were out to sea, but the faults that moved were too small to get all the way to the surface and cut the sea floor and create a tsunami. The aftershocks from these earthquakes are also too small to cause a tsunami. An earthquake at sea usually needs to be greater than magnitude 6.5-7 for the fault to cut all the way up through the rocks to the sea floor to cause even a small tsunami.
No. The Japanese tsunami was created by a big earthquake fault just offshore of Japan called a subduction zone fault, where one tectonic plate is being pushed under another tectonic plate. These subduction zone faults can cause very big earthquakes (magnitude 8+) and very big tsunamis, like the 2011 Japanese tsunami or the 2004 Indian Ocean tsunami. There is a subduction zone fault off the east coast of the North Island, which could create a big tsunami there, but there is no subduction zone fault off the Canterbury coast that could create such a big tsunami here.
Christchurch City Council has confirmed a budget for tsunami warning sirens and is currently working through the process of installing them. They should be installed by the end of June 2012. When installed these sirens will not be used for a local tsunami because there will not be time to sound the sirens.
Sirens will only be used in the event of a distant source tsunami from across the Pacific Ocean, and possibly for a regional source tsunami from the Hikurangi subduction zone if there is time. There will not be time to sound the warning sirens if there is a local source tsunami in Pegasus Bay – earthquake shaking will be your ONLY warning.
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