An earthquake expected “in the foreseeable future” 70 years after the Adelaide tremors

Adelaide has a stable climate that rarely causes widespread destructive weather, but beneath the surface lies serious danger.

The City of Churches is the most earthquake-prone of Australia's capital cities.

The last major earthquake, which at the time was the most damaging on record in Australia, was in 1954.

The 5.4 magnitude earthquake on March 1 caused three serious casualties, damaged more than 3,000 buildings, and led to about 30,000 insurance claims for collapsed or cracked walls, chimneys, and broken windows.

A University of Adelaide news release showing the front cover of The News on the day of the 1954 Adelaide Earthquake. (Source: The News/University of Adelaide)

Professor Alan Collins of Tectonics and Earth Systems at the University of Adelaide said another major event would almost certainly occur in its lifetime.

“Whether it happens this year, or in 10 to 15 or 20 years, who knows, but it's likely to happen in that kind of time frame – that is, in the foreseeable future,” Professor Collins said.

The university's School of Civil and Environmental Engineering estimated in 2011 that if a repeat of the 1954 earthquake occurred in Adelaide that year, it would cause $1 billion in damage.

Active area

Adelaide is the most seismically active area in Australia.

There are a number of faults that run beneath the greater Adelaide area, including the Willunga Fault to the south of the city, the Barra Fault to the north, and the Eden-Burnside Fault, which runs from near Seacliff to the Hells Face area.

Alan Collins moved to South Africa because of the sites of geological interest in Adelaide and the Flinders Ranges. (Supplied: Alan Collins)

Professor Collins said there was a fault running through Bonython Park towards Thebarton Theatre, “and the line crosses into the new tunnel they are digging”.

“This is also an active fault, so they definitely had to take that into account when planning the new tunnel [for the Torrens to Darlington project]”.

The country itself lies on top of the Indo-Australian tectonic plate, which includes the Indian subcontinent and about half the area of ​​New Zealand, and moves about 7 centimeters northeast every year.

“As we move north, we're being pushed by a ridge in the middle of the Southern Ocean, just south of Adelaide, and we're grinding into another plate and all that force is going through the plate,” Professor Collins said.

“We're in a weak zone within that plate, so when the forces get big enough from us grinding down those other plates, the weak rocks under Adelaide break and we create the Lofty Ridge, which is exactly why it's so high.”

Evidence of the Willunga Fault near Silex Beach, south of Adelaide. (ABC Radio Adelaide: Malcolm Sutton)

He said the Lofty Mountain Range had been built up over about three million years by earthquakes, which can push the ground up by a meter or two in short bursts of force.

“It's creeping up too, but the main reason for that is because of those earthquakes, and the intermittent nature of the ground breaking,” Professor Collins said.

Beachport shook in 1897

While the 1954 earthquake remains the most devastating ever seen in the state, the strongest was a 6.5 magnitude quake near Beachport in 1897.

Earthquake activity shakes Adelaide again

The city of Adelaide was rocked by two notable earthquakes in one month during the year 2022. A senior seismologist referred to a “group of events” and said there were several influencing factors.

The Advertiser reported on 11 May 1897: “A house at Wangolina, between Kingston and Robe, has been destroyed, and an infant has been injured during the ravage.”

“The reports from Beechport are most alarming, as the post office and telegraph station there have been destroyed, most of the chimneys knocked down and the ground opened up on Main Street, though the extent of the 'hole in the ground' has not been determined.”

More recently, on 16 April 2010, a 3.8 magnitude earthquake struck the Adelaide Hills from Mount Barker, shaking homes from the hills to the coast and making its presence felt as far away as Kangaroo Island.

The Australian Geosciences Foundation considered it a “larger than usual” earthquake along the fault line, where earthquakes are expected.

Latest tremors

South Australia has experienced 126 earthquakes this calendar year so far, including three with magnitudes higher than magnitude 4 – two south-east of Hooker and one in the Lake Eyre region.

In 2024, there were 137 earthquakes, including a magnitude 4.2 quake in Jamestown and a magnitude 4.1 northwest of William Creek. In 2023, there were 88 earthquakes, including a 4.7 magnitude earthquake in the Flinders region.

Between January 1 and December 10 this year, South Africa experienced 126 earthquakes. (Supplied: Australian Geosciences)

Jonathan Griffin, a seismologist at the Australian Geosciences Centre, said there was no real reason there would be more or fewer earthquakes on average in the region.

“It's a random thing, like flipping a coin, sometimes you'll get three heads in a row,” he said.

“There have been six earthquakes greater than magnitude 4 in the past five years.

“If we go back to a time when records were very good since 1960, we had 96 earthquakes in the state greater than magnitude 4, so it's a similar rate over the long term.”

Griffin said that a high or low number of earthquakes on average did not indicate that a large quake was imminent.

“However, when you experience a moderate to large earthquake, you tend to experience aftershocks afterward, so having one earthquake means you are likely to experience another in the next short period of time,” he said.

Cactus Canyon at Silex Beach shows strong evidence of the Willunga fault. (ABC Radio Adelaide: Malcolm Sutton)

He said that sometimes there was a “foreshock” — an earthquake that preceded a larger quake — but it was more common for aftershocks to occur after a large quake.

Mr Griffin was also of the opinion that Adelaide would be hit by another major earthquake in the foreseeable future.

Low to moderate risk.

The Department of Planning, Transport and Infrastructure, in its Critical Infrastructure and Earthquake Risk Handbook, states that the risk of earthquakes in Adelaide is “low to moderate” on a global scale.

“However, by Australian standards, Adelaide has the highest risk of all capital cities,” she added.

“Seismologists indicate the possibility of earthquakes of up to 7.5 Richter magnitude in South Australia.”

DPTI said in its 2019 brochure that the Mount Barker earthquake served as a reminder that events must “take into account the owners and managers of the state's critical infrastructure.”

Although Adelaide has a high level of seismic activity, the country's worst earthquake struck Newcastle on 28 December 1989, killing 13 people and hospitalizing 160. Its magnitude was 5.6.

The 1954 Adelaide earthquake had a magnitude of 5.4.

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