Tsunami Information

A tsunami is a set of huge and powerful waves that are caused from an under sea disturbance, such as an earthquake, an under water landslide or a volcanic eruption.
The large waves travel in different directions from the main cause of disturbance. The waves after the disturbance move in a circle outwards and go in all different directions just like ripples.


Tsunami are recorded in Australia about once every two years, and most are small and present little threat of land inundation to our coastal communities. However the abnormal waves, tides and currents caused by even relatively small tsunami can be dangerous to swimmers and mariners.
As a result of the Australian Tsunami Warning System (ATWS) Project, jointly undertaken by the Bureau of Meteorology (Bureau), Geoscience Australia (GA) and Emergency Management Australia (EMA) and funded by the Australian Government, Australia now has a comprehensive, independent tsunami warning service to advise the media, public and emergency authorities of any tsunami threat to Australia and its offshore territories.

In order to assist the community, tsunami threat levels in Regional Tsunami warnings are categorised into three levels with required community responses; these have been determined in consultation with emergency management authorities. These Threat Levels will be specified for the same coastal areas that are used for routine Bureau Coastal Waters Forecasts, already known to marine users.
  1. No threat: An undersea earthquake has been detected, however it has not generated a tsunami, or the tsunami poses no threat to Australia and its offshore territories.
  2. Marine and immediate foreshore threat: Warning of potentially dangerous waves, strong ocean currents in the marine environment and the possibility of only some localised overflow onto the immediate foreshore.
  3. Land inundation threat: Warning for low-lying coastal areas of major land inundation, flooding, dangerous waves and strong ocean currents.


The waves can travel up to 805 kilometers per hour on a unprotected sea.
As the tsunami reaches the shallow water it begins to rise up and it grows to great heights and will violently smash into the shore. Tsunamis can grow to the height of 30.5 meters (100 feet). They can be mistaken for 'tidal waves' but tsunamis have nothing to do with the tide.



References:

http://www.bom.gov.au/tsunami/index.shtml

http://www.fema.gov/kids/tsunami.htm
http://environment.nationalgeographic.com/environment/natural-disasters/tsunami-profile/

by gurbano and nodea