The Australian coastline is at risk of facing destructive tsunamis predicts Australian geology and emergency services.
Simulations show 9.0 earthquake in Indonesia could devastate Christmas Island and parts of northern WA.
A 9.0 earthquake in New Zealand could send powerful waves into Sydney and Brisbane.
Following the catastrophic 2004 Boxing Day tsunami and last year's devastating Christchurch earthquake, the Joint Australian Tsunami Warning Centre operated by the Bureau of Meterology and Geoscience Australia have simulated two wave-triggering earthquakes in training exercises.
The 'worst case' scenarios were of a tsunami triggered by an Indonesian 9.0 earthquake, which sent 5-10 metre waves into Christmas Island, while powerful waves also hit the populated coast between Sydney and Brisbane from a simulated New Zealand quake.
The data showed the tsunamis would take five hours to reach the mainland from either earthquake.
Centre Director Chris Ryan said because Australia is in the middle of a tectonic plate, far away from the active edges, the energy released by the tsunamis would be distributed over a wider front by the time it reaches the coast.
"For Australia's coasts we only need to worry about the higher magnitude events because of our distance from the source, and then only some of the possible earthquake sources are close enough, or oriented in the right direction, to send a severe tsunami towards Australia" he said.
"In a sentence, the exercise scenarios are not likely, but they could happen tomorrow," he added.