Loud rumbles and shaking windows woke hundreds of residents across Adelaide in the early hours of Saturday but the cause of the disturbance remains a meteorological mystery.
Geoscience Australia said more than 800 people across the Adelaide region reported the rumble.
Geoscience Australia initially said there was a 1.4-magnitude quake near Mount Compass but retracted that a few hours later, saying there had actually been no earthquake.
More than 800 residents, including Laurie in Pooraka, reported feeling two tremors, describing windows rattling and floors shaking at 2:05am Saturday and again at 2:15am.
“No noise whatsoever. [I] just felt the really harsh shudder and it felt like it was coming through in a line from west to east,” he said.
“It ran for five or six seconds and then was gone.”
Geoscience Australia said the cause was most likely large thunder claps as the tremors were not seen widely on seismometers.
Bureau of Meteorology forecaster Matt Collopy said there were storms in the region overnight and conditions meant loud sounds would travel.
“I have had a bit of a look at the data from the lightning detection system and there certainly was lightning pushing across,” he said.
“The other thing to note is, with this thick level of mid-layer cloud, so slightly higher cloud, the sound does travel quite substantially.”
Seismologist David Love said the tremors could have been an unknown meteorological disturbance but further investigations would be needed to discover its cause.
There were no reports of injury or damage but many Adelaide residents, such as Howard from Marion, remained unconvinced of the storm theory.
“What alerted me was the windows rattling and you don’t get that with thunder,” he said.
Photo ABC News: Tom Fedorowytsch