Tsunami warnings explained: Marine threat to Australia after Tonga eruption

The BoM says the size of the waves means the threat is for the marine environment, but there is potential for land impact on Lord Howe Island and Norfolk Island.

What is a marine warning?

No threat is when 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.

Marine and immediate foreshore threat is a 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 is a warning for low-lying coastal areas of major land inundation, flooding, dangerous rips, waves and strong ocean currents.

How often do tsunamis occur?

Tsunamis are recorded in Australia about once every two years, the BoM says.

“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.”