Tsunami

A tsunami is a series of powerful waves with strong currents. They are mostly caused by underwater or coastal earthquakes and sometimes by underwater landslides or volcanic eruptions. Tsunami can threaten lives, property and infrastructure.

For more information about tsunami, go to: ORC Natural Hazards

If you are near the coast, remember, if an earthquake is Long or Strong, Get Gone!

Once the shaking has stopped, go immediately to higher ground or as far inland as possible.

The three types of tsunami

There are three distinct types of tsunami. The type you encounter depends on the distance you are from the place where it is generated.

  • Distant tsunami: Are generated from a long way away, such as from across the Pacific in Chile. In this case, we will have more than three hours warning time for New Zealand.
  • Regional tsunami: Are generated between one and three hours travel time away from their destination. An earthquake centred on the Puysegur Trench, off the coast of Southland could trigger a regional tsunami.
  • Local tsunami: Are generated very close to New Zealand. This type of tsunami is very dangerous because we may only have a few minutes warning

Tsunami Warnings

Warning messages and signals about a possible tsunami can come from several sources – natural, official or unofficial.

  • Natural warnings: For a local source tsunami which could arrive in minutes, there won’t be time for an official warning. It is important to recognise the natural warning signs and act quickly.
  • Official warnings: Official warnings are only possible for distant and regional source tsunami. Official warnings & advisories are issued by the National Emergency Management Agency (NEMA) to the national media, local authorities, and other key response agencies. An Emergency Mobile Alert (EMA) may be issued if there is a threat of flooding to land areas.
  • Other advice including what zones to evacuate from will be issued by Emergency Management Otago or your district Council through their website, social media, tsunami sirens (if installed), EMA, mobile text, loud hailer or other local arrangements.
  • Unofficial or informal warnings: You may receive warnings from friends, other members of the public, international media and from the internet. Verify the warning only if you can do so quickly. If official warnings are available, trust their message over informal warnings.

Tsunami Evacuation Zones in Otago

If you live or work near the Otago coastline, you should be aware that there is always a risk of a tsunami from an undersea earthquake. We have prepared an interactive map that shows the areas that should be evacuated in the event of a tsunami. Check the evacuation zones on the map and work out the best route for you and your family to take if you need to leave your home.

You can view the Otago tsunami evacuation zones here

Get Ready for Tsunami

Before a tsunami

  • Check if you are in a Tsunami Zone and know the evacuation zones in your area.
  • Plan multiple evacuation routes for you and your whānau. It is important to do this before rather than during a tsunami emergency. Regularly practise your tsunami hikoi (evacuation walk)
  • Have a Grab Bag ready – If you have to evacuate think about what you might need if you are away from your home for several days.

What to do if there is a risk of tsunami

Learn the natural warning signs that a tsunami may be coming:

  • Feel a long or strong earthquake (“Long” means the shaking lasts more than 1 minute, “strong” means the shaking is so severe, it is difficult to stay standing)
  • See a sudden rise or fall in sea level
  • Hear loud and unusual noises from the sea

Don’t wait for an official warning….

  • Go immediately to the nearest high ground or as far inland as possible, taking the route that is quickest for you. Do not stay at home. If possible, run, walk, cycle when evacuating from a tsunami, you don’t want to get stuck in a tsunami zone. If driving, keep going once you are well outside the evacuation zone to allow room for others following you.
  • Don’t go to the beach or river to watch
  • Listen to the radio and follow any instructions
  • Stay away from exposed areas until the official all clear is given by authorities

Following a tsunami

  • Only return home when you have been told it is safe to do so by official source such as Emergency Management Otago or other emergency services
  • Stay away from coastal water, tidal estuaries, rivers, and streams for at least 24 hours after any tsunami or tsunami warning , as even small waves can create dangerous currents. There may be debris in the water for weeks following a tsunami.
  • If there was an earthquake, expect aftershocks. Aftershocks may generate another tsunami so be prepared to evacuate again.
  • Stay away from damaged areas. You might hamper any rescue operations, cause further damage or put yourself at risk.