Australia could be hit by an earthquake as strong as the one that hit New Zealand on Saturday, and we may not know when and where it might happen, a Geoscience Australia seismologist says.
No country is immune from earthquakes, but the continent’s location in the middle of the Australian plate, away from the boundaries of tectonic plates where most seismic activity occurs, has allowed it to avoid the destructive tremors experienced by its neighbours.
But there are faultlines within Australia – some of them millions of years old – and we do not know which are active and which are causing the earthquakes, Geoscience’s senior seismologist Clive Collins said.
“There is no real reason to believe that we won’t get a large one anywhere,” he said.
While researchers can look to historical records to glean statistics on where previous earthquakes occurred, the data only goes back 150 years and so not all faultlines are mapped.
“That’s one of our major problems,” Mr Collins said.
“When you know where your faultlines are, and you know they are active, you can then forecast when we might get more earthquakes or [learn] what earthquakes we had in the past.”
Geoscience Australia researchers have travelled across the country in recent years to search for signs of previous large quakes, finding broken surfaces in Western Australia, Central Australia, Victoria and NSW, Mr Collins said.
“We are very certain some of these must have caused very large earthquakes – comparable to what happened in New Zealand on the weekend.”
But the size of the country means it could take years for faultlines to be discovered.
The seismic information collected by Geoscience is added to the earthquake hazard map of Australia, which in turn feeds into Australian building codes.
And strict building codes that require structures to withstand earthquakes are believed by experts to be what helped New Zealand avoid the high death tolls experienced by other countries that recently experienced similarly strong jolts.
Haiti – which was hit by a strike-slip fault that caused a 7.0 magnitude quake last January – suffered the loss of at least 220,000 lives.
New Zealand, which also experienced a strike-slip fault between the Pacific plate to the east and the Australian plate to the west, recorded no fatalities.
Only two people were seriously injured.
New Zealand sits on the so-called “Ring of Fire”, the boundary of the Australian and Pacific tectonic plates, and experiences up to 15,000 tremors a year.
It averages at least one a day that is magnitude 4.0 or stronger.
In Australia in the past decade, nearly 3600 earthquakes have been recorded – about one a day.
Statistically, Australia is considered to be the safest from destructive earthquakes, which have killed hundreds of thousands of people in Asia and South America in recent years.
One of Australia’s most devastating tremors was the 1989 Newcastle quake, which claimed 13 lives and measured 5.6 on the Richter scale.