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Why are there earthquakes in Australia?

This morning, residents in south-eastern Australia felt the earth shake beneath them for about 20 seconds.

The magnitude-5.9 earthquake was centred 10km under Mansfield, 129km from Melbourne. Two later shakes, understood to be aftershocks, registered at magnitudes of 4.0 and three.1.

Gary Gibson, a seismologist on the College of Melbourne, advised ABC Radio that it was the largest earthquake skilled in Victoria since European settlement.

Mansfield mayor Mark Holcombe advised ABC Breakfast that “it got here proper out of left subject. We don’t have earthquakes, that I’m conscious of. Not one of the locals I spoke to this morning had that have with earthquakes right here earlier than, so it’s one proper out of left subject. It was only a actually massive crumble.”


Learn extra: Tectonic Timelapse


Earthquakes happen when continental plates shake or tremor as fault planes transfer. This occurs as a result of stress under the crust builds up and ultimately tries to flee, which forces the plates to maneuver to accommodate.

 There are three alternative ways the plates can transfer to trigger an earthquake:

  • Strike-slip: Two sides of the airplane transfer horizontally to one another
  • Regular: One fault tries to maneuver downwards
  • Reverse: One fault strikes on high of the opposite.
Three varieties of plate motion. A) Strike-slip, B) Regular, C) Reverse. Credit score: Wikimedia commons.

Land plenty alongside continental plates, comparable to New Zealand (Aotearoa), are riddled with main fault traces as a result of the continents aren’t linked. This implies they’ve frequent earthquakes.

Australia, nonetheless, is in the midst of a big continental plate, known as the Indo-Pacific Plate, so there are far fewer small fault planes and no main fault traces. This implies massive earthquakes are unusual.

The final earthquake of the same measurement in Victoria was a 5.5-magnitude quake in 2009, however the largest earthquake recorded in Australia – magnitude-6.7 – was in 1988, south-west of Tennant Creek within the Northern Territory.

Tectonic plate boundries. Credit score: Wikimedia commons.

There are nonetheless some fault planes in Australia, however they aren’t very massive. These fault planes are extra like cracks within the floor fairly than two separate plates shifting towards one another.

The stress under the crust continues to be attempting to launch and escape, which suggests Australia experiences frequent tiny earthquakes so deep within the earth that we barely really feel them. They’re additionally too small to alter the panorama.

Nevertheless, when an enormous quake happens, like this morning, it’s usually as a result of the stress builds as much as the purpose that it ‘pushes’ up the crust, inflicting a reverse fault. If there’s sufficient stress, this will typically elevate the land, which, over time, might turn into a mountain. For this reason there are mountainous areas in Victoria – they have been brought about as stress compelled minor faults to maneuver and elevate. There are numerous mountains round Mansfield as a result of it’s the situation of a minor fault airplane, so it isn’t too shocking that it was


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https://cosmosmagazine.com/earth/earth-sciences/why-are-there-earthquakes-in-australia/ | Why are there earthquakes in Australia?

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