© ABCThe quake struck Mount Barker, in the Adelaide Hills, about 11:27pm ACDT (Google Maps)
The earthquake happened at 11:27pm and people living within a 50 kilometre radius of the quake reported tremors lasting for up to 15 seconds.
The epicentre was close to Mount Barker, 40 kilometres east of the capital, in the Adelaide Hills.
Mount Barker resident Robert says he heard a loud bang when the quake struck.
"We heard a terrific explosion," he said.
"We live right opposite the golf course and lots of galahs roost in the trees and they made nearly as much noise as the earthquake itself but it was definitely an explosion."
Paul in Bridgewater emailed ABC News Online, saying: "Whoa! We just had what seemed like an earthquake go through our house."
Meanwhile, Steven from Moana said: "Several of my neighbours came out into the street and said that their houses shook like mine did. It lasted for about 10 to 15 seconds."
There have been no reports of injuries or damage to buildings in the capital.
David Jepson, a seismologist from Geoscience Australia, says while tremors in the region are not unexpected, this quake was larger than normal.
"This would have been felt quite widely, up to about 50 kilometres from the epicentre, and we've had a number of felt reports from the region," he said.
"That's basically shown that it has been felt quite widely across Adelaide city."
David Love, a seismologist with the South Australian Department of Primary Industry and Resources, says further activity along the fault line cannot be ruled out.
"This is probably the largest earthquake near the Adelaide area for quite a long time, possibly in excess of 20 years," he said.
"An earthquake that size will give a fair shake near the epicentre, its certainly enough to wake people up, but most unlikely to cause much other than that.
"There is a chance of more activity, I think the chance is fairly low, but we can't rule it out."
Mr Love says data is still being collected but the event appears to have occurred more than 15 kilometres below ground.
"From the reports that have been coming in it looks like it may have been a relatively deep earthquake therefore lessening the effects immediately above it on the surface," he said.
The quake was felt around Adelaide and more than 100 kilometres north of the city as well as on Kangaroo Island.
I felt the house shaking here in Allenby Gardens! I heard a rumbling sound first & got up to turn the television sound down and thats when I felt the house and floorboards shaking. Reminded me of when someone is using one of those paving wakers/vibrating machines, very quick vibrations. By the time I walked to bathroom and then back to kitchen, the shaking had stopped. I noticed a few distant rumbling sounds afterwards on and off, but it was so distant I could barely hear them.
I realised we might have had an earthquake, so called my mum and said : Did you just feel that? My mum and grandmother did not feel or hear anything, and they are only just up the street from my house, they were in Flinders Park.
My 2 dogs and cat did not react in any way. Unusual for my husky as he freaks out with thunder. But all the crickets outside were suddenly chirping and it sounded like there were hundreds of them in my back yard that night after quake.
It would be interesting to find out how many more suburban areas outside from Mt. Barker, in Adelaide actualy experienced the shake.
Thanks for the write up on this Earthquake!
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