Explainer: how to prepare for a tsunami

The recent magnitude 7.1 earthquake and subsequent tsunami warning in northern New Zealand reminds us that tsunamis are unpredictable and can strike any time.

If you live in a tsunami risk zone then you’re probably aware of what to do when a tsunami strikes. But if you’re a traveller or a visitor from somewhere not used to such events, how can you prepare yourself?

Since the devastating Sumatra earthquake and tsunami of December 2004, it has been recognised that there is risk of tsunami along all coastlines.

A tsunami can strike any coast at any time and we can’t predict exactly when or where they will occur.

Tsunamis are most often caused by undersea earthquakes but they can also be caused by submarine landslides or volcanic eruptions.

A tsunami can move as fast as a jet plane across the open ocean and can smash into land with waves as high as 20 metres.

The water may wash inland for several kilometres in flat lying areas, and can move up streams and rivers, picking up everything in its path.

Waves may continue to strike the shoreline for many hours, and dangerous currents can continue for days following the event.

Although a tsunami can’t be prevented, its impact can be lessened when communities understand the risks, receive timely warnings and know how to respond.

Understanding the level of risk for your area is the first step towards being prepared. If you are travelling, look up the national disaster management centre or emergency response agency for your destination.

Natural and official warnings

Warning messages about tsunamis can come from several sources.

Natural warnings include feeling a strong earthquake, seeing a sudden rise or fall in sea level, or hearing a loud and unusual noise from the sea. In many cases this means a tsunami could arrive in minutes and it is important to act quickly and not wait for an official warning.

Official warnings are distributed by local authorities such as police, civil defence or local councils. Warning messages are often circulated through media channels including television, radio and the internet.

Tourist areas may also have sirens along some beaches.

What is important to note is that each country, and in many cases each local area, will have a different warning system. So when you travel somewhere new, do not assume it will have a system that is similar to what you are used to from other places you have travelled, or at home.

If you receive an official warning, act quickly and follow the instructions to move to higher ground.

There are a number of free and subscriber services for tsunami warnings, but don’t rely on SMS or email warning services. During an earthquake or tsunami these services often become overwhelmed and messages don’t get through.

Being prepared

Before you travel, find out what you can about the tsunami risk in the area you are visiting.

Subscribe to official travel advice from your government, if available. Organise comprehensive travel insurance and check that you are covered for natural disasters such as tsunami.

On arrival, perhaps as you check into your hotel, ask your host about how tsunami warnings are disseminated and where the tsunami evacuation routes are.

Find out where the nearest high ground is (at least 20 metres above sea level) and work out how you get there. If there is no high ground nearby, find out if there are established vertical evacuation routes. These are usually tall, concrete-reinforced buildings with at least four storeys.

During a tsunami

Stay out of the water and away from beaches and waterways. Never go to the shore to watch the tsunami. If you can see it, you are too close to escape.

Use TV, radio or internet to get updates on the situation, but try to keep phone lines clear for use by emergency personnel.

Follow instructions from local officials to move to higher ground or evacuate into a tall building. Evacuate on foot or by bike and drive only if essential. Roads tend to become gridlocked during a tsunami emergency, making it more difficult for the emergency response teams to access the area.

Stay away from at-risk areas until the all clear is given. The first tsunami wave may not be the last or the largest, and the waves may be more than an hour apart.

After a tsunami

Do not return to the evacuation zones until advised by authorities, even if you can’t see any damage. Be aware that there may be extensive earthquake or flood damage and buildings may not be safe.

Look out for broken power lines and other dangers and stay away from beaches and waterways.

If you are overseas, then as soon as you are able, contact your local embassy, High Commission or consulate in case family and friends are trying to find you. Stay informed through conventional or social media if phone lines are overwhelmed.

We can’t predict or prevent tsunamis, but the good news is that you can improve your chances of staying safe by understanding the risk, being prepared and acting quickly when disaster strikes.

Further reading

Australian Geographic’s The 10 most destructive tsunamis in history

International Tsunami Information Center