These fault planes are more like cracks in the surface rather than two separate plates moving against each other. The pressure below the crust is still trying to release and escape, which means Australia experiences frequent tiny earthquakes.
Usually, they are so deep in the earth that we barely feel them. This causes a reverse fault. In fact, the mountains in Victoria were caused as pressure forced minor faults to move and elevate. You can help Geoscience Australia by making a report if you felt the earthquake here. Originally published by Cosmos as Why are there earthquakes in Australia?
Deborah Devis is a science journalist at Cosmos. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most.
Please support us by making a donation or purchasing a subscription today. Share Tweet. Because Australian earthquakes occur only in the top 20 km, one dimension of the rupture area is constrained. A typical site in Australia will be within 50 km of a magnitude 7 event every , years or so.
In active areas like Japan, Philippines or California, earthquakes of magnitude 7 occur every few years. The activity in these places is restricted to a much smaller area than that of Australia, so a typical site may be within 50 km of a magnitude 7 event every years or so. Low seismicity does not mean weak ground motion. It means that strong earthquake motion happens less often. Earthquakes of magnitude 8 and larger are termed great earthquakes, and normally only occur at plate boundaries.
These are unlikely to ever occur within Australia. Earthquakes of magnitude 9 and larger will rupture faults for hundreds of kilometres, so usually only occur on subduction zones such as along the west coast of South America, or the south coast of Alaska. As seismic waves radiate away from an earthquakes, their amplitude decreases due to geometric spreading.
In addition, some energy may be absorbed within the rocks, especially in soft or hot rocks. The rocks in Western and Central Australia are old, relatively cold, and hard, so seismic waves are not greatly attenuated by absorption of energy.
The rocks in Eastern Australia are younger and softer, and absorb energy at a rate that is about world average or greater. Aside from properly designing buildings, there are steps people can take to avoid injury during an earthquake. Victorian earthquake explained: why did it happen and why was the impact relatively mild?
Why did it happen? Read more. Quick Guide How to get the latest news from Guardian Australia Show Email: sign up for our daily morning briefing newsletter App: download the free app and never miss the biggest stories, or get our weekend edition for a curated selection of the week's best stories Social: follow us on YouTube , Facebook , Instagram , Twitter or TikTok Podcast: listen to our daily episodes on Apple Podcasts , Spotify or search "Full Story" in your favourite app.
Topics Victoria Earthquakes explainers. Reuse this content.
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