Queensland has been hit by two earthquakes in quick succession, one of them the strongest in almost a century and coming just two days after a similar-sized tremor in the region.
And seismologists have warned more may follow.
Geoscience Australia said a magnitude 5.7 quake struck at 1:38pm Saturday, with its epicentre 110 kilometres due east of Fraser Island at a depth of 10 kilometres.
Another earthquake, measuring magnitude 5.2, was registered in the same area just over an hour later, at 2:46pm.
Senior seismologist Dan Jaksa said the first quake on Saturday was the biggest to hit the state since 1918, and 10 to 20 times stronger than the magnitude 5.3 quake that struck south-east Queensland on Thursday.
"This is equivalent to the earthquake that occurred in 1989 in Newcastle, which of course is the most damaging earthquake in Australia's history," he said.
Mr Jaksa said it was quite common for earthquakes to occur in quick succession.
"This is simply the event of (three) days ago seems to have triggered another part of the fault to release its stress and it's certainly done that," he said.
"This is not a high area of earthquake seismicity in terms of its frequency but Australia sits on a intra-plate, we're not on a plate boundary like New Zealand.
"So we get them in a bit more of a random pattern, which actually makes them a little bit more dangerous, because we don't expect them in Australia, but they do and can occur."
Queensland Fire and Emergency Services said there were no reports of damage so far.
The Bureau of Meteorology said there was no tsunami threat.