What to do
Areas are generally at greater risk if they are less than 7 m above sea level and within 2 km of the shoreline.
Waves can reach 10 m or more – 30 m in extreme cases. They can move inland several hundred metres depending on the slope of the ground, and often the first wave is not the largest.
Tsunamis can travel up rivers and streams, and also wrap around islands impacting coasts not facing the source. Post-tsunami flooding and strong wave currents can last for several hours.
Before a tsunami
- Have working emergency equipment – such as flashlights, battery-powered radios, and first-aid kits – as well as supplies – such as canned foods, medication, and clean water – ready and at hand.
- Prepare a safety backpack including medicine and first-aid items.
- Keep evacuation plans in visible spots at home, work, and other places.
- Prepare an emergency plan including each member of your household.
- Teach and practice your evacuation plan with all household members – everyone needs to know what to do in case not all members are together.
- Ensure that all household members recognise natural tsunami signs – official tsunami warnings may not be issued in time.
- Identify vulnerability of key locations (home, workplace, school) by discussing it with your local disaster management office.
- Be aware of concrete, reinforced multi-storey buildings nearby that can be used for evacuation to upper floors.
- Identify danger zones, assembly locations, designated evacuation routes, or the quickest way to reach higher ground safely with the help of your local disaster management officials – a safe assembly location would be at least 30 m (100 ft) above sea level and 3 km (2 mi) inland.
- Look to insure your house in case of tsunami-related damages and flooding.
- Learn how to turn off the gas and electricity in your home.
- Keep important documents in water-proof containers in high places.
Sensing a tsunami
In case you encounter any of these, head to higher ground immediately – a tsunami may arrive before any official warning.
A very strong or long earthquake? Local earthquakes may cause tsunami waves to arrive within minutes after the shaking stops.
A sudden rise or fall of sea level? The ocean recedes as waves build, exposing reefs, rocks, and fauna on the sea bottom.
A strange or loud sound coming from the sea? Approaching tsunami often create a loud “roaring” sound similar to that of a train or jet aircraft.
To higher ground or as inland as possible. Don’t wait for official evacuation orders, leave low-lying coastal areas immediately.
Dos & Don'ts
DO
- Get to higher ground or move inland if you recognise any tsunami signs.
- Head to an upper floor (at least a 3rd storey) or roof of a concrete and reinforced building if higher ground isn’t an option – climb a strong tree as a last resort.
- Look for something to use as a raft if swept up by a tsunami.
- Follow official guidance and stay out of danger zones until an all-clear is issued – tsunamis can last for hours.
DON’T
- Wait for an official warning if you sense a tsunami – waves may arrive before any is issued.
- Go down to the shore to watch for a tsunami.
- Leave safe zones after an initial wave – tsunamis are never a single wave.
- Try to surf a tsunami.
When on vessels
Tsunami waves are barely felt in the open ocean (deeper than 100 m), but trying to head out may be more dangerous depending on the type of tsunami:
- For local tsunamis (generated within 100 km away), leave your boat behind and head to higher ground as soon as possible;
- For tele-tsunamis (generated over 1,000 km away), listen for official tsunami wave-arrival time estimates before trying to move to deeper waters.
Do not return to port after a tsunami has passed – it may have damaged port facilities. Dangerous wave activity or currents in and around harbours may continue for hours, debris may also be present.
Keep in contact with harbour authorites or listen to mariner radio reports to know how to act.
After a tsunami
Stay tuned to the latest emergency information. Once the all-clear is given:
- Help injured or trapped people and call for help if necessary;
- Keep out of stagnant water;
- Open windows and doors and remove moist mud to help dry buildings;
- Stay out of damaged buildings;
- Check food supply and discard all food that has come in contact with flood water;
- Check for damage to sewer and water lines and test drinking water;
- Return home only when authorities say it's safe to do so.
Warning levels
Now that you know more about how to identify an incoming tsunami and what to do and not to do, learn more about the different warning levels or messages authorities may issue in your area.