Earthquakes in Australia: How big are they and how prepared are we?

Most of us tend to associate earthquakes with places like New Zealand, California or Japan.

These sites lie at the edges of tectonic plates, where the pressure of the plates rushing against each other causes rocks deep in the Earth suddenly to fracture and slide into each other, creating an earthquake.

But what about earthquakes in Australia?

Well, it’s already happening, as evidenced by today’s 5.8-magnitude earthquake, which was felt in different parts of southeastern Australia.

Seismology explained

Earthquake seeds are located in the tectonic plates that make up the Earth’s surface and on which the continents sit.

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Trevor Allen is a seismologist at Geoscience Australia who is working to determine the potential for catastrophic earthquakes to affect Australian communities.

Because Australia is in the middle of a tectonic plate, the earthquakes we see are a little different from other places, he says.

Dr. Allen Pavlova uses it to describe why earthquakes occur in Australia.

“Imagine, if you will, that the tectonic plate looks like the Pavlova Plate — with a thin, brittle crust lying on top of a ductile layer, but mostly a hard meringue mantle,” says Dr. Allen.

“The Australian continent will sit in the middle of our Pavlova.”

Quake can be considered like Pavlova, although the latter is more pleasant.

Pexels: Adrian Frentescu

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If you put your hands on the edge of the Pavlova and begin to squeeze, the crust around your hands will be the first to break, like those earthquakes at the boundaries of tectonic plates.

But if you keep pressing, the stress will eventually build up in the center of the crust, and cracks will start to appear.

This is similar to how earthquakes occur in Australia.

“The same forces that drive earthquakes at tectonic plate boundaries play a role – they take longer to appear in the center of Pavlova,” says Dr. Allen.

Painting margins are close to Australia. The black dots are the foci of individual earthquakes. (

Supplied: USGS

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Australia actually experiences an earthquake about once a day, but the most damaging earthquakes – above 5 degrees – are usually seen only twice a year.

But Dr Allen says it is extremely unlikely that Australia will experience an earthquake of magnitude 8 or 9.

That’s because the necessary forces only occur at the plate boundary, where the plates can snap together and disintegrate with tremendous force.

“We don’t have faults large enough or active enough for these large earthquakes that we see at plate boundaries to occur,” says Dr. Allen.

“Overall, the seismic rates we see here in Australia and in other stable tectonic regions are about a hundred times lower than those in the plate boundary regions.”

What major earthquakes have occurred?

Australia experiences about 80 earthquakes of magnitude 3 and greater annually, although the vast majority are small.

Australia’s largest recorded earthquake of magnitude 6.6 on the Richter scale was in sparsely populated Tennant Creek, NT in 1988. Two earthquakes of the same size followed within 12 hours and aftershocks are still recorded today.

Sgt. Mark McAdy inspects the damage after the Tennant Creek earthquake. (

Athena Avianos, Courtesy of Tennant and District Times

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An earthquake measuring 6.5 on the Richter scale struck the small town of Meekring in West Westbelt in 1968, devastating the city with a 37-kilometre rupture and a vertical deformation of 2-3 meters from one side of the fault to the other.

One of the most significant earthquakes in Australia was the 5.6-magnitude Newcastle earthquake that occurred on a December morning in 1989.

It was not so great in size, but because it was located near the city, it caused great destruction and injury, and 13 people were killed.

Nine of those people were killed in the collapse of the Newcastle Workers’ Club, which was due to hold a concert that night with thousands of attendees.

“It doesn’t take much imagination to see that the consequences of that day could have been so much worse had the earthquake only been a few hours later,” says Dr. Allen.

The Newcastle Workers’ Club was badly damaged during the earthquake that struck Newcastle on 28 December 1989 (

Newcastle area library collection

When will we get another one?

Even in areas of high seismicity, there is no perfect tool for earthquake prediction.

Space for play or pause, M for mute, left and right arrows for searching, up and down arrows for volume. Listening Duration: 11 minutes 33 seconds 11 minutes

Fault lines and historical events can help scientists determine the likely locations of earthquakes in the future.

But an earthquake can also occur in an unexpected location on an undetected fault.

“Despite our best forecasting efforts, no part of Australia is immune from shaking the ground with the force of earthquakes,” says Dr. Allen.

There are quite a few more active Australian fault lines located near major urban centres, particularly near Adelaide and Melbourne.

An earthquake in these locations could be catastrophic and disrupt the lives and livelihoods of many Australians.

These events are extremely rare, but this does not mean that they cannot occur in our lives.

Meekering Hall after the 6.5 magnitude earthquake in 1968 (

Supplied: Western Australia State Library

How can we prepare for a major earthquake?

Given our inability to predict where the next big earthquake will strike, how prepared are we to deal with if it will occur in a densely populated area of ​​Australia?

Ensuring that structures are built to withstand earthquakes is an important step.

“The best defense against earthquakes is strong building codes, and compliance with those codes,” says Dr. Allen.

Structural engineer Michael Griffiths is developing ways to make old buildings less vulnerable to earthquake damage.

“Most major buildings in Australia were erected…before earthquake forces were taken into account,” says Dr. Griffiths, a researcher in bushfires and natural hazards CRC.

The iconic Christchurch Cathedral was destroyed during the 2011 earthquake in Christchurch, New Zealand. (

AFP: Mark Baker

)

In 1995, after the Newcastle earthquake, the Australian Building Code introduced earthquake design requirements.

This means that any modern construction must have a significant amount of resistance inherent in it.

“They may be damaged economically beyond repair, but they shouldn’t collapse and kill anyone,” says Dr. Griffiths.

He says the main danger is the old, unreinforced brick buildings.

Many street facades in our capital have two- to three-story buildings with large ornate brick facades.

“[They] They are very attractive and really provide a lot of ambiance for the area, but these are the types of buildings that were hit hardest in Christchurch after the recent earthquakes,” says Dr. Griffiths.

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Many of the dead from the 2010-2011 Christchurch earthquake were people outdoors and injured by falling construction work.

Dr. Griffiths would like to see more work in strengthening the existing buildings, so that in the event of an earthquake, there is minimal damage and loss of life.

“As the decades go by, more and more of those old buildings will be gradually demolished and replaced with modern construction that complies with modern laws,” says Dr. Griffiths.

“But right now, there are quite a few buildings that are fairly vulnerable.”

How can people protect themselves?

If you happen to find yourself in an earthquake like today, Dr. Allen has some advice on what to do.

His best advice is to “fall, cover, and catch.”

Hide under a sturdy table or desk if you can, and keep waiting until the shaking stops.

The goal is to protect yourself from any flying debris or furniture.

Damage to Broome Kitchen Store from the earthquake in July 2019. (

Supplied: You must

)

“Don’t go into the hallway – he’ll probably shut the door and break your nose,” he says.

“Don’t try to get out of the building – in the event of a strong earthquake, you won’t be able to walk, let alone run!”

A great way to feel prepared is to participate in GreatShakeOut, the world’s largest earthquake drill, on October 21.

And if you feel any tremors, tell Geoscience Australia with a felt report.

This will help provide important information to emergency services and first responders in the event of a devastating earthquake anywhere in Australia.

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