Tsunami - Ready and Able
Understanding the link between earthquakes and tsunami has made it possible to establish tsunami warning systems. A warning system involves recording two sets of data: seismic activity and changes in sea levels. Real-time data from seismic stations will indicate if an earthquake has occurred and automatic analysis will indicate the likelihood of a tsunami.
Not all earthquakes cause a tsunami, so another set of information is required. Sea-level readings are gathered from a number of buoys in the ocean or coastal gauges to work out if a tsunami has occurred and to monitor its path. If a tsunami is verified, communities can be warned.
The Pacific Tsunami Warning System was established in 1949. It is made up of a network of seismic monitoring stations and sea-level gauges. These detect earthquakes and abnormal changes in sea level and help scientists decide whether a tsunami has been triggered by an earthquake. If so, warnings go out to many countries and regions in the Pacific. A warning centre is located in both Hawaii and Alaska.
In Australia, there is the Joint Australian Tsunami Warning Centre (JATWC) operated by the Bureau of Meteorology and Geoscience Australia. The Centre is based in Melbourne and Canberra. It was established to give Australia an independent capability to detect, monitor, verify and warn the community of the existence of tsunami in our region and possible threats to Australian coastal locations and offshore islands. JATWC operates 24 hours a day, seven days a week.
There are three main warning levels:
- Watch - stay tuned for updates
- Marine warning - strong waves and currents and perhaps some localised run-up, and
- Land warning - foreshore and nearby land flooding is highly likely, with dangerous rips, waves and strong ocean currents.
Australian tsunami warning system
An undersea earthquake causes displacement of both the seafloor and the sea surface, and the spreading out of seismic waves (in red). The disturbance in the sea surface radiates outwards as a tsunami, which travels much slower than the seismic waves. Once the seismic waves are detected by distant (usually land-based) seismometers, sea-level data from coastal tide gauges or DART buoys are analysed to determine whether a tsunami has actually been generated (Source: Geoscience Australia)
If you hear that a strong undersea earthquake has occurred, stand by for a possible tsunami warning. You should be prepared to move from low-lying coastal or lakeside areas to high ground at short notice.
Remember that tsunamis are potentially dangerous and destructive. At no time should you move closer to the shore to watch a tsunami.
Look out for tsunami natural warning signs.
- Feel the earth shake? A large undersea earthquake may be felt before the arrival of tsunami by an ongoing shaking of the ground in coastal regions. However, you may not feel an earthquake if the event is far away.
- See ocean water disappear from the beach, bay or river? Before a tsunami, water may, but not always, recede from the shoreline before returning as a fast-moving wall of water. This is known as a drawdown. 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 roar approaching (a bit like a jet aeroplane or a train), tell your family and friends. It may be a tsunami approaching.
Action to take
Run to higher ground if you think there may be tsunami approaching. If you see a wall of water coming or hear a tsunami warning, leave low-lying coastal areas immediately. Move away from the water and move quickly inland towards higher ground.
When an official warning has been issued
When the Joint Australian Tsunami Warning Centre (JATWC) issues an official warning, it means a tsunami has been detected. They will consult with State or Territory emergency authorities to determine appropriate response for the public. The emergency authorities have a plan in place for a range of emergencies. If a tsunami was heading for Australia and it was known ahead of time, the emergency authorities would distribute warnings on the radio and television stations to let people know to move away from the danger zones.
A phone number, 1300 TSUNAMI (1300 878 6264), is also available for the public to listen to tsunami warnings for Australia and the Bureau of Meteorology’s website displays relevant tsunami warnings and information.
You should follow the instructions of your local emergency authorities if you are asked to evacuate. Head for higher ground and away from the beach or rivers that lead to the beach.
Remember that a tsunami is not a single wave and stay out of danger areas until an official 'all-clear' has been issued.
Never go to the shore to watch a tsunami. If you can see it, you are too close to escape.
Remember to wait until the emergency authorities inform you it is safe to return to the affected area. Be careful, as strong waves, currents and abnormal sea levels may still affect some beaches, harbours and waterways for hours or even days afterwards.
The Attorney-General's Department and Questacon have developed a tsunami 'Choose-Your-Own-Adventure'- style game. This game was developed to teach school-aged children important safety messages about tsunami. This game is also housed within the Awesome Earth Exhibit at Questacon in Canberra. To order the game on CD, please contact email@example.com.