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Explained: What really caused Adelaide's phantom earthquake

If you were in Adelaide and felt the earth move overnight, you were not alone.

But experts are adament: That was not an earthquake.

Meteorologists say the rumble that shook half the state was caused by a rare weather phenomenon.

The source of the 'earthquake' was traced to the Gulf St Vincent after early explanations failed. Photo: 7 News
The source of the 'earthquake' was traced to the Gulf St Vincent after early explanations failed. Photo: 7 News


Just after 2am two shockwaves about 10 minutes apart shook South Australia.

Geoscience Australia was quick to call it a 1.4 magnitude quake and ground zero was near Willunga.

A vineyard at McLaren Vale was initially identified as the epicentre of the earthquake but after further investigation GeoScience Australia removed it from its website.

The nearest neighbour had no doubt.

"Definitely not thunder 'cause I didn't hear any rain, I didn't hear any thunder," they said.

Seismologists recorded vibrations from Hambley Bridge to Hindmarsh Island.
[36936587|Meteorologist Matt Collopy said sonic booms explained the tremors. Photo: 7 News/]

Meteorologists say what everyone heard and felt were sonic booms caused by thunder from lightning strikes in the Gulf St Vincent, which were trapped under a huge blanket of cloud.

"The thunder that normally resulted occured but that sound was trapped underneatyh that layer and therefore travelled further and sounded louder," meteorologist Matt Collopy said.