This Aussie city could be at risk of “devastating” earthquake
While excavating two large trenches to the south of Adelaide, researchers have discovered the city is at risk of an earthquake 30 times more powerful than the 2011 Christchurch quake that killed 139 people.
Experts from Geoscience Australia, the University of Melbourne and the University of Sydney uncovered evidence of huge quakes that predate local records while excavating along the Willunga fault.
“We calculate the 55km active length of this fault could potentially host an earthquake as large as magnitude 7.2,” geologist Dr Dan Clark told Adelaide Now.
“An earthquake of this size would involve approximately 30 times the energy released by the earthquake that devastated Christchurch.”
We're working with @unimelb & @ausquake to find evidence of ancient #earthquakes on the Willunga Fault to better understand the seismic risk to #Adelaide. 👉▶️ to hear from our Earthquake Geologist & check out 👉 https://t.co/BEOI52E3zz. #GACommunitySafety #DisasterRiskReduction pic.twitter.com/8i2VtMMcDx
— Geoscience Australia (@GeoscienceAus) June 8, 2022
Though earthquakes are a rare experience for most Australians, Adelaide is one of the country’s most seismically active areas. The city straddles two major faults, with the Para Fault running under the CBD and the Eden Fault sitting beneath the city’s eastern suburbs.
In the last decade, 10 quakes exceeding the “minor” level of 3.0 on the Richter scale have occurred within 150km of the city. The largest, a 3.7 tremor, was recorded in March at Mt Barker.
As for the rest of the country, “moderate” tremors above 5.0 occur once every one to two years, while one “strong” tremor scoring above 6.0 will hit once every ten years on average.
“Big quakes clocking above 6.0 don’t often happen close to populated areas in Australia thankfully,” Adam Pascale, Chief Scientist at the Seismology Research Centre, told news.com.au.
“Earthquakes are very unpredictable though - we could get one in the Blue Mountains in NSW for example next week.”
Dr Pascale added that modern buildings were constructed to withstand moderate tremors, but there is still plenty that isn’t earthquake resistant, exemplified by the series of quakes in Victoria last year.
“There’s a lot of infrastructure in our major cities,” Dr Pascale said, adding that Perth and Melbourne were also on the list of “chief candidates” for future tremors.
Though the excavation, which saw researchers study the layers of sediment displaced by past quakes to estimate the magnitude of future ones, found that there was a minor but real risk of a “big one” in the future, Dr Clark said a massive quake “might occur once every few tens of thousands of years”.
“A magnitude of 6.2 of the size of the Christchurch earthquake, for instance, might happen every thousand years or every few thousand years,” he explained.
As reassuring as the odds of a quake striking now might be, Dr Clark did warn that moderate shakes, like Adelaide’s famous 1954 tremor, could be as frequent as once a century.
“We haven’t seen in most places in Australia the largest earthquakes that can be generated,” he said.
“Critical infrastructure, facilities and the community, in general, should be prepared for these events, even if they are very infrequent.”
Image: Geoscience Australia