Geoscience Australia said that the earthquake hit in an area known as Macquarie Rise in the Pacific Ocean, about 800km off the coast of Tasmania.
The epicentre was 400km off Macquarie Island.
Seismologist Cvetan Sinadinovski said that this was one of the most active areas in the world, with large earthquakes common every one or two years.
“This was an inter-plate earthquake between the Indo- Australian and Pacific plate and earthquakes of this size can be felt for up to 1500km,” he said.
“There was no danger to structures anywhere because the quake struck so far off the coast.”
Mr Sinadinovski said that many reports from people who felt the effects of the the quake were received from Southern Tasmania and isolated phone calls from around the State.
He said that in terms of energy, the earthquake was 30 times larger than the 1989 Newcastle earthquake.
“If a quake that size happened underneath a population centre in Australia, it would have been devastating in its effect and could have destroyed a whole city,” he said.
Australian scientists working on the remote Macquarie Is. in the sub-Antarctic were unaware of the earthquake, the Australian Antarctic Division said.
“Nobody felt anything,” AAD spokesman Tony Press said.
Prospect resident Sue Francis said she was up sitting in an armchair watching TV just before 2am when she felt the effects of the earthquake.
“All of a sudden I felt a distinct jolt and the floor sort of waved sideways,” Miss Francis said.
“I thought `oh my God here we go again,’ because I’ve felt one before here to the extent I think the house might be on a fault line.” She said she had previous experience with earthquakes while living in Wellington, New Zealand.
Legana resident Peter Fleming felt the quake.
“I got up to go to the toilet and when I got back into bed the house started to creak structurally and the bed started to rock,” he said.
“My wife slept through it and thought I was kidding this morning when I told her about it until she turned on the news and heard the story about the whopper 8.1 earthquake.”
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