Ways you may hear about tsunami
Official Tsunami Watches, Tsunami Warnings, No Threat Bulletins and Tsunami Cancellations and Tsunami Warning Summaries are issued by the Joint Australian Tsunami Warning Centre
Tsunami Warnings will indicate a threat level that indicates whether tsunami are likely to:
- affect the marine and immediate foreshore;
- cause land inundation of low lying coastal areas, or
- pose no threat to an area
No Threat Bulletin
To advise people that the earthquake has been assessed and that no tsunami threat exists.
In the first stage seismologists determine that there is the potential for an identified undersea earthquake to cause a tsunami threat to Australia. If there is no threat, a National Tsunami No Threat Bulletin will be issued.
To advise people that a tsunami threat may exist and that they should look out for further updates.
In the first stage seismologists determine that there is the potential for an identified undersea earthquake to cause a tsunami threat to Australia. If there is a threat, the Bureau will issue a National Tsunami Watch.
To advise people that a tsunami threat does exist and to advise them of the level of threat and action they should take.
If sea level observations and further data confirm the tsunami threat, or if any potential first point of impact is less than 90 minutes away, the Bureau, on behalf of the JATWC, will use its severe weather communication infrastructure to issue Tsunami Warnings for the States and Territories under threat.
Marine and Immediate Foreshore Threat
Warning of potentially dangerous rips, waves and strong ocean currents in the marine environment and the possibility of only some localised overflow onto the immediate foreshore.
Land Inundation Threat
Warning for low-lying coastal areas of major land inundation, and flooding, dangerous rips, waves and strong ocean currents in the marine environment.
Tsunami Warning Cancellation
When the main threat has passed or if a tsunami didn't eventuate, the Bureau will issue a Tsunami Watch Cancellation or Tsunami Warning Cancellation. The relevant State or Territory emergency authority will inform the public when it is safe to return to the affected area.
Natural Signs of Tsunami
In Australia you may receive an official Tsunami Warning, however it is also important to be aware of the natural warning signs:
- FEEL the earth shake. If you are near the ocean and you feel the ground shake, a strong earthquake may have occurred and possibly caused a tsunami. However, you may not feel the earth shake if the earthquake occurred long way away.
- SEE the ocean drop. Before a tsunami arrives, the ocean level may (but not always) drop dramatically before returning as a wall of water. If you notice that the water is disappearing, tell your family and friends and prepare to move to higher ground.
- HEAR an unusual roaring sound. If you hear a loud roaring sound from the ocean (a bit like an aeroplane or a train), tell your family and friends. This sound may be heard before a tsunami arrives.
How are Tsunami Warnings issued?
Tsunami Watches, Warnings, No Threat Bulletins and Tsunami Watch or Warning Cancellations can be issued in a number of different ways. Warnings may not always be issued using all of these methods.
You should always act early based on the first warning you hear.
The sources of tsunami warning could include:
Radio and television broadcast
Radio and television broadcasts are the most common communication tool to inform the public of a Tsunami Watch or Warning. These may be preceded by the Standard Emergency Warning Signal (SEWS).
Tsunami Warning Siren
If you are on or near a public beach, a siren like warning may be activated by Surf Life Saving NSW or council lifeguards. People in the water, or the immediate foreshore area may be instructed to evacuate and move away from the area.
A text or recorded message on your phone
A text or recorded voice message may be sent to people in the affected area. Once this message has been received, it is then advised that people follow the steps to safety. People should not wait for this message if they have heard it via other sources.
Low flying aircraft equipped with public address systems.
Aircraft with the ability to fly lower than normal may be tasked to disseminate warnings. This would be coordinated by the NSW SES.
Advice may come from other government agencies, emergency services and authorised persons
While the JATWC are the authoritative agency for Tsunami Warnings, local authorities and other government agencies can be a way of issuing advice on tsunami. You should also continue to listen to the radio for further advice and do not return to the evacuation zones until authorities have given the all-clear.
Two-way radio / Marine Satellite Phone
UHF CB, marine VHF radios and where appropriate marine satellite phones may also be used to advise marine users of any warnings.
Warnings issued by the Joint Australian Tsunami Warning Centre will also be shared via NSW SES social media including Facebook and Twitter. Other agencies and local community organisations may also share warnings with their audience as well.
National Tsunami Warning Summary
To provide the public, media and emergency authorities with the status of tsunami warnings nationally.
Sample of a Tsunami Warning:
The blue area indicates the areas to be affected by the marine and immediate foreshore threat, while the green area shows the areas that are predicted not to be affected by the tsunami.
Below is a sample of the safety advice that may accompany a Tsunami Warning issued by the Joint Australian Tsunami Warning Centre