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Earthquakes aplenty: Australia’s shifting tectonic plate causing constant tremors

Donna Coutts, June 7, 2018 6:15AM Kids News

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A machine called a seismograph or seismometer, which measures and records earthquake tremors. media_cameraA machine called a seismograph or seismometer, which measures and records earthquake tremors.

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Australia is on shaky ground, with hundreds of earthquakes every year. Just this week, there have been at least seven.

But you probably didn’t notice them and they are rarely anything to worry about, according to the government’s earthquake centre, Geoscience Australia.

Geoscience Australia senior duty seismologist* Daniel Jaksa said they don’t often cause any damage.

“We have the most of any part of the world but ours are small,” he said.

Seismologists such as Mr Jaksa measure earthquakes on a scale of magnitude*. There’s about one earthquake a day in Australia with a magnitude of 2.0. The biggest ever recorded earthquake was in Chile, South America, in 1960, which had a magnitude of 9.6.

The Earth’s crust is made up of big plates, called tectonic plates. It’s a bit like an eggshell with a few big cracks in it. Australia sits on the middle of one of these plates. Countries that are on the edge of plates are more likely to have massive earthquakes. We have more earthquakes than any other area that sits on the middle of a plate.

The reason for the frequent earthquakes is that the plate we are on is moving.

“As the core* of the Earth cools the heat is pushed outwards and the energy from the heat pushes the crust around,” Mr Jaksa said.

“The plate we are on moves 7cm every year towards the north or northeast.”

A map showing where an earthquake happened in Indonesia. Picture: supplied media_cameraA map showing where an earthquake happened in Indonesia. Picture: supplied

Australia’s most active earthquake zone, also called a seismic zone, is in the Wheatbelt region of southern Western Australia. Another is the Flinders Ranges in South Australia.

“Have a look at the Flinders Ranges on Google Maps and you can actually see it bending and changing in all different directions,” Mr Jaksa said.

The size of an earthquake determines* how far away it can be felt.

“A magnitude 8 earthquake in Indonesia could be felt in Adelaide,” he said.

A man walks amid the rubble of destroyed buildings in Port-au-Prince following the earthquake that rocked Haiti on January 12, 2011. Picture: AFP media_cameraA man walks amid the rubble of destroyed buildings in Port-au-Prince following the earthquake that rocked Haiti on January 12, 2011. Picture: AFP

Timing is everything when a big earthquake strikes.

Mr Jaksa compared two earthquakes of the same size to explain.

“A magnitude 6 earthquake in Western Australia in 1968 happened in the middle of the morning when most people were out and about in the fields farming. The Christchurch (New Zealand, 2011) earthquake was the same size but it happened at lunchtime when everyone was out in the streets on their lunchbreak.”

Mr Jaksa said being inside buildings is one of the safest places to be when a small or medium earthquake happens.

“The area five metres around the outside of a building is the most dangerous zone*,” he said.

A map showing the impact of the 1989 Newcastle Earthquake. media_cameraA map showing the impact of the 1989 Newcastle Earthquake.

EARTHQUAKES BIG AND SMALL

The biggest recorded earthquake was 9.6 magnitude in Chile, South America, in 1960.

The next biggest was in Alaska, US, in 1964.

The biggest recorded earthquake in Australia was magnitude 6.6 in Tennant Creek, Northern Territory in 1988.

The 1989 Newcastle earthquake was magnitude 5.6 and killed 13 people.

Here’s a snapshot of just the past week in Australia:

  • 2.9-magnitude quake near Pingelly, WA and a 2.0-magnitude quake near Canberra yesterday
  • 2.5-magnitude quake near Peterborough, SA and a 2.4-magnitude quake near Dalwallinu, WA on Monday
  • 2.6-magnitude quake at hawker, SA, on Sunday
  • 2.0-magnitude quake at Frogmore, NSW, on Saturday; and
  • 2.4-magnitude quake near Mornington, Victoria, last Wednesday

You can see recent earthquakes by visiting Geoscience Australia’s website earthquakes.ga.gov.au

GLOSSARY

seismologist: earthquake scientist

magnitude: size

core: centre

determines: decides

zone: area

LISTEN TO TODAY’S STORY

QUICK QUIZ

1. How many earthquakes are there in Australia each week?

2. Where was the biggest-ever-recorded earthquake?

3. Where is Australia’s most active earthquake zone?

4. Where is the most dangerous place to be during an earthquake?

5. How big and what year was the Tennant Creek earthquake?

CLASSROOM ACTIVITIES

Create a diagram, or set of diagrams with labels that would help another student understand how and why earthquakes happen.

Time: Allow 30 minutes

Curriculum Links: Science

Extension: In the story you have read some safety tips about earthquakes. Create a storyboard or a script for a video or TV advertisement that will help people know what to do if they are in an earthquake. Include a song and a slogan so people can remember the most important points.

Time: Allow 45 minutes

Curriculum Links: Media Arts

VCOP ACTIVITY

After reading the article, with a partner, highlight all the openers you can find in blue. Discuss if they are powerful and varied openers or not. Why do you think the journalists has used a mix of simple and power openers? Would you change any, and why?

IN ONE SENTENCE, TELL US WHAT YOU FOUND MOST INTERESTING IN THIS STORY

Do not use one-word answers. Use lots of adjectives.

Extra Reading in science