What is a tsunami?
When there is an earthquake in the open ocean, shockwaves caused by the earthquake can produce series of fast-moving waves or surges, known as tsunamis, that can move at speeds of between speeds of 600–700 km/hr towards land.
When these tsunami waves hit the shallower areas near the coast they can behave like storm surges, suddenly increasing in height and speed.
Depending on their speed and amount of water they are carrying, tsunamis can cause significant damage and loss of life by quickly pushing debris such as trees, building materials, vehicles, and boats further inshore.
- Watch this video on how tsunamis work (Youtube)
It's important to know which parts of Porirua are most likely to be affected by a tsunami, so check out our map below
Tsunami evacuation zones
Porirua Tsunami Evacuation Zones interactive map
The red zone is the beach and marine environment, and some very low lying areas. This area is the one we ask people to stay out of most often as a result of smaller tsunamis. Evacuate this area when instructed to, or immediately after any long or strong earthquake.
The orange zone is the area we may evacuate for a large earthquake in the Pacific, such as near South America, causing a tsunami wave of up to 5 metres at the Wellington coastline.
The yellow zone is the self-evacuation zone which means if you feel a long or strong earthquake, then get yourself out of all zones. This zone has been defined by modelling of earthquakes on the subduction zone to the east of the North Island, the worst case scenario for the Wellington region.
It's vital that you know the tsunami evacuation routes from where you live, work and play.
Visit the New Zealand ShakeOut 2022 website to find out all you need to know about this year's Tsunami Hikoi on 27 October.
All of New Zealand is at risk of earthquakes and all of our coastline is at risk of tsunamis. We can’t predict when earthquakes and tsunamis will happen, but you can help protect yourself and your family by knowing if your property is in a tsunami evacuation zone and what you need to do.
In an earthquake
- Drop, cover, hold – this makes you a smaller target, stops you being knocked over and protects your head, neck and vital organs.
If you are near the coast and in a tsunami zone
- If it’s long or strong be gone – if you feel an earthquake that rolls for more than a minute OR makes it hard to stand up, don’t wait for a tsunami warning as there may not be time for one in your area. Move to high ground or as far inland as you can. Walk if you can. Stay there until you get the all clear.
- Know where to go, find out who can help you and who might need your help .There are no tsunami blue lines in Porirua – take the time now to find out where you need to evacuate to.
What is the warning signal?
The earthquake might be your only warning. If you are in a coastal area and experience a long OR strong earthquake, it's hard to stand up, or you observe strange sea behaviour such as the sea level suddenly rising or falling, or hear the sea making loud and unusual noises or roaring like a jet engine, do not wait for an official warning. Take immediate action when the shaking stops and self-evacuate to the nearest high ground. Listen to your local radio station for more information.
For a distant sourced tsunami, we receive warnings through the National Warning System, which is the official warning system for New Zealand. It uses information from the Pacific Tsunami Warning Centre. Once received, these warnings are broadcast on public radio, and usually on television. Check the Ministry of Civil Defence and Emergency Management website to see if your phone is capable of receiving Emergency Mobile Alerts.
Will there be a tsunami siren?
No, Porirua does not have tsunami sirens. The Titahi Bay and Plimmerton fire sirens are not used for a civil defence emergency. Some Council vehicles have mounted PA systems playing a warning message. These vehicles may circulate some key areas of the city as necessary.
If you hear anything unusual such as messages over a loudspeaker, tune into a local radio station, or check our homepage to see if there is anything you need to know about.
What are the local radio station frequencies?
The radio station frequencies for Wellington/Hutt Valley, Porirua are:
- National Radio (Radio NZ) 567 AM, 101.3 FM, 101.7FM, 104.5 FM
- Newstalk ZB 1035 AM
- Classic Hits 90 FM
- More FM 94.7 FM, 100 FM
- The Breeze 94 FM, 98 FM
- Radio Live 98.7 FM, 1233 AM
You can also sign up to receive emergency alerts to your iOS and Android devices through the Red Cross Hazards App.
Plan now
- Find our which evacuation zone you are in and make a plan with your family about what to do after an earthquake. You need to do this for your home, school, work place, or anywhere you frequent that might be in the tsunami zone.
- Know where to go, find out who can help you and who might need your help.
- Have a grab bag handy with essential items, so you can leave without delay. Remember, you might not get back into your house, so consider a USB stick or similar with scans of important documents, photos etc.
- Evacuate on foot and go to friends or family outside the evacuation zones (roads can get jammed with traffic easily).
- Do not pass through an evacuation zone to get home or collect your children from school or childcare – they will have their own evacuation systems if needed.
- During an emergency, local police, fire, and emergency services officials are trying to save your life. Give them your fullest cooperation.
- Never go down to the beach to watch for a tsunami. The wave moves much faster than you can run.
