Where the Earth shakes in Australia

17 October 2018

Communities in the Wheatbelt in Western Australia, Gippsland in Victoria and the Australian Capital Territory are more likely to experience earthquake ground shaking than other parts of the country according to latest update to the National Seismic Hazard Assessment (NSHA) for Australia.

The first update to the NSHA since 2012 was officially released today by Geoscience Australia at the inaugural Australian Geoscience Council Convention in Adelaide.

Senior seismologist Dr Trevor Allen said although Australia is not usually associated with large, damaging earthquakes, on average, 100 earthquakes of magnitude 3.0 or larger are detected across the country each year.

"It's impossible to accurately predict exactly when and where an earthquake will occur but the history of earthquake activity in a region can tell us a lot about its potential risk for future earthquakes."

Dr Allen said regularly updating the NSHA helps Australian communities prepare for future earthquake events.

"The NSHA provides key information to the government agencies and regulators, so buildings and infrastructure design standards can be updated to mitigate the impact of strong earthquake ground shaking."

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National Seismic Hazard Assessment of Australia map.

Dr Allen said consistent with previous assessments, the Wheatbelt in Western Australia continues to be one of the regions with the highest estimated seismic hazard.

"The Wheatbelt has high rates of historical seismicity, including the 1968 magnitude 6.5 earthquake near Meckering.

"We estimate Wheatbelt communities could expect to experience a magnitude 5.0 earthquake every 10 to 25 years."

Dr Allen said some of Australia's most active faults are located in Gippsland's Latrobe Valley and Strzelecki Ranges, which have the potential to host a very large earthquake and contribute to elevated  seismic hazard estimates at longer timescales.

"The Gippsland region has relatively high rates of natural seismicity and we estimate a magnitude 5.0 earthquake in the region every 25 to 50 years.

"Fault sources in the Gippsland region contribute to earthquake ground shaking hazard with return periods of 500 years and longer. These are typical return periods used to guide the design levels for buildings and infrastructure.

"Outside of regional Australia, Canberra is now the capital city with the highest estimated seismic hazard. This is due to its proximity to both the Lake George and Murrumbidgee faults, which that contribute to its long-term hazard forecast and its moderate levels of historical seismicity."

Dr Allen said an increase in underlying data used in the NSHA resulted in Geoscience Australia revising the estimated seismic hazard for Canberra.

"The underlying data used to inform this update has increased since the 2012 assessment, as has our confidence in certain modelling decisions, such as adjustments to historical earthquake magnitudes and improvements in modelling seismic sources.

"What we look at when we're updating the NSHA is how and why levels of ground shaking vary across Australia and the likelihood that these levels will be exceeded in a specific time period.

"There is always more to learn when it comes to earthquakes in Australia. Science and technology is constantly evolving and improving and the NSHA is updated regularly to ensure it incorporates best practice and evidence-based science.

"In regions like the Wheatbelt and Gippsland with higher seismic hazard, it is an essential tool for developing mitigation strategies that make at risk communities more resilient."

Dr Allen said earthquakes can still occur in unanticipated locations where we may not have many historical observations.

"Although we cannot predict the exact day, time and place of a large, damaging earthquake, we can apply best practice and evidence-based science to make sure communities are as prepared as possible."

For more information or to arrange interviews, please email media@ga.gov.au or call the Geoscience Australia 24 hour Media Hotline on 1800 882 035.