Australia not earthquake free

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Newcastle NSW 1989

I remember this one well, though the effects in Sydney were minor. My father had just died and I was in my mother’s room in her Glebe Point old people’s home, on the phone making funeral arrangements. “Shit! An earthquake!” I recall saying inadvertently to the person on the other end of the line as the room distinctly shook.

My father, mother and I were living in West Wollongong in 1973 when a magnitude 5.5 earthquake struck in the early hours of the morning. Not only were we shaken but the noise was amazingly loud. The ceiling was damaged in one room at The Illawarra Grammar School where I was teaching at the time, the local radio station was off the air for several minutes, the lights went out at the Steelworks and in the coal mines – that would have been scary – and a large crack appeared in the front of the Department of Education building in Wollongong. One woman reported being thrown out of bed and afterwards laughed that this was a rather extreme way for her boss to make sure she got up early enough for work. At TIGS we joked that the quake was a “punishment” for the previous night’s rather pleasant wine tasting in the very room that was damaged; the Reverend Gentleman who founded the school was of evangelical persuasion and his portrait had fallen off the wall in presumed disapproval. The epicentre of that quake was out towards Picton/Appin. There is an active fault in that region.

There are several active faults in Australia, but we are far from the edges of tectonic plates so earthquakes such as those in the Pacific rim of fire are unknown here. Nonetheless a 2002 report says “two separate geological studies have concluded that an area from Adelaide to south-east Victoria is seismically active and the next ‘big one’ could endanger lives and infrastructure.”

Contrary to the popular notion that Australia is an ancient continent that has for millions of years been geologically comatose, University of Melbourne geologists have uncovered evidence that parts of South-eastern Australia recently stirred from their geological slumber and are in an active mountain building phase. These mountains are being shaped by earthquakes, some reaching greater than 6 on the Richter scale.

"When these big quakes reoccur, they have the potential to cause catastrophic damage to cities such as Melbourne, Adelaide, and the La Trobe Valley area, which straddle some of these major faults lines," says Professor Mike Sandiford, who conducted one of the studies.

Possibly, the most dramatic indication of this geological stirring, which the studies estimate began suddenly about ten million years ago, can be found in the landscape of the Mount Lofty Ranges near Adelaide.

"Some faults around Adelaide have moved slabs of the continent up to 30 metres in the last one million years," says Sandiford.

"A typical earthquake of magnitude 6.0 might produce a displacement of about one metre. Thirty metres is equivalent to 30-50 big earthquakes in the last million years," he says…

The Meckering Earthquake (Western Australia) in 1968 (magnitude 6.8) is the biggest recent one in Australia.

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Meckering 1968

See also Geoscience Australia and List of earthquakes in Australia.

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