The chance of Australia having a catastrophic earthquake in the future
Thousands reported feeling terrifying shakes after the 4.8-magnitude earthquake struck near Muswellbrook, NSW on Friday.
Roofs caved in, stock was sent falling from supermarket shelves and hundreds of thousands of locals have been left shaken and confused after a 4.8-magnitude earthquake struck NSW on Friday.
Thousands of Aussies reported feeling the effects of the quake across an area spanning hundreds of kilometres — all the way from south of Sydney up to the NSW mid-north coast. The earthquake hit Denman, around three hours north of Sydney in the upper Hunter region, just after 12pm, with locals in the area and surrounds left in amazement, and many in disbelief at what had occurred.
LIVE ROLLING COVERAGE: Sydney rocked as 4.8 magnitude earthquake strikes NSW
The Bureau of Meteorology insists there is no tsunami threat so far and NSW Police said, as yet, there's been no reports of major infrastructural damage buildings, and no reports of injury. Here's what you need to know.
What you need to know
A 4.8 magnitude — initially reported as 5.0 — struck Denman near Muswellbrook, 243 kilometres north of Sydney in NSW, just after midday on Friday.
Dozens of reports of minor damages to retail stores have emerged, but police say there's been no major infrastructural harm to buildings in the area. And no reports of serious injuries.
The epicentre was near Muswellbrook but tremors were felt by residents in places as far away as Coffs Harbour, Sydney and Canberra.
Schools near the epicentre have been evacuated and a community put on alert, with 2,500 customers in the area having lost power, according to Ausgrid.
The SES said they are making house calls to dam owners in the area to ensure their integrity.
What causes earthquakes?
When heat from the Earth's core creates currents in the crust, the tectonic plates can scrape together, bump, or drag along each other. This is what causes an earthquake, and why the surface sometimes cracks.
Tectonic plates are always slowly moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth's crust and cause the shaking that we feel.
Is NSW on a tectonic plate line?
NSW is a part of the Australian continental plate, one of a series of tectonic plates on Earth, but it does not sit on a tectonic plate boundary. Current estimates of earthquake risk in the Sydney Basin indicate that on average, there is a 10 per cent chance of ground accelerations exceeding 0.11g in a 100 year time frame. To put that in some context, 0.001g is only just perceptible, 0.02g will cause people to lose their balance while 0.50 is movement of a very high intensity but well-designed building will survive if the duration is short.
Could Australia ever have a catastrophic earthquake?
Australia is mostly protected from major earthquake events — as it it doesn't sit on a tectonic plate boundary — however, while significant earthquakes are relatively rare in the country, they certainly occur and have done in the past.
What was the worst earthquake Australia ever had?
The most catastrophic earthquake in Australian history also took place in the Hunter region, in Newcastle in 1989. A total of 13 people were killed and there was an estimated damage bill as high as $4 billion.
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