Experts warn that Australia is complacent about the earthquake disaster

[ad_1]

“When my wife and I first came back to Melbourne from Christchurch, we were dreading going everywhere, to be honest.

“We’ve seen unreinforced masonry. We’ve seen a lot of those big, overhanging awnings, the kinds you see when you walk down Smith Street or Brunswick Street.” [two popular inner-north 1890s shopping strips] that go out onto the road.

“We know that these things just collapse and fall onto the road in earthquakes; we know that the front of a lot of those brick buildings collapse when strong ground motions are forced upon them.”

More than 26,000 Victorians – and some Tasmanians – have submitted a ‘felt report’ to Geoscience Australia following Sunday night’s earthquake. Earth Sciences Australia

Professor Quigley said Melbourne “dodged a bullet” in the 2021 earthquake which caused widespread damage to buildings, but no personal injuries, because the city was in a state of COVID-19 lockdown.

“We know this is a lesson we’ve learned for centuries, and there are a whole range of retrofit techniques that can be done to reduce the likelihood of these types of failures occurring.

“One of the lowest hanging fruits is just doing more work to identify the highly vulnerable structures that will collapse in future earthquakes and kill people.”

He agreed that there was complacency about earthquakes in Australia.

Experts say the city’s inner awnings would be vulnerable to collapse in the event of a major earthquake.

“There is a widespread perception that potentially devastating earthquakes in Australia are rare.

But compared to similar geological areas [known as stable continental regions] Professor Quigley said Australia is among the most seismically active countries.

Dr Trevor Allen of Geoscience Australia led the development of the 2018 National Earthquake Risk Assessment for Australia. He said the southeastern corner of Australia is considered a “seismic hot spot”, with an earthquake of magnitude 5.0 or greater occurring every seven years on average in Victoria.

Professor Quigley noted that since 1960 Australia has experienced 10 earthquakes similar to the Christchurch earthquake, every six to 20 years on average. The most catastrophic was the 1989 Newcastle earthquake, which killed 13 people and caused $4 billion in damages.

Australia’s crust amplified the vibration

Professor Quigley said the strong Australian crust enabled destructive seismic waves to travel farther and cause greater shaking intensity compared to areas that were located on plate boundary areas, such as New Zealand.

“I think we’re seeing very large earthquakes in Australia and the evidence is staring us right in the face,” he said.

“It’s all over the place. We have fault fissures, for example, between Melbourne and Geelong. We have faults on the Mornington Peninsula. We have faults under Melbourne.”

We know that these faults can generate earthquakes of magnitude five, magnitude 6 and larger. So the scenario whereby an earthquake of the magnitude of Christchurch occurs in Melbourne is perfectly plausible. one hundred percent.”

In a 2021 joint paper, Professor Quigley noted that many of Australia’s largest cities were in Newtectonic Rift Zones. One of the capital cities’ greatest seismic hazards is Canberra. 80 percent of large dams in Australia lie within 100 km of recent tectonic faults.

“When combined with population densities in areas with lower seismic Building Code standards, compared to more seismically active countries, and compromised infrastructure, damage and loss of life in an Australian earthquake below one of our urban centers could significantly exceed what would be expected for a similar earthquake. with great force in several plate boundary zones in socio-economically comparable countries,”

He said fault lines were modified after the earthquakes, causing aftershocks and new tremors.

Insurance companies are using the wrong tools

“Earthquakes cluster in time and space. Certainly, large earthquakes increase the likelihood of smaller earthquakes.

“So for an earthquake like the one that just happened, we might expect a magnitude 3 aftershock, which will also be felt. We might expect several magnitude 2 earthquakes, maybe 10 to 15 to 20 while the crust settles.” “.

Prof Quigley said complacency with earthquake risk meant insurers were using outdated shaking maps to determine liability.

“The actual earthquake shaking intensity can be much higher or much lower than the value for a whole host of reasons.”

He said insurance inspectors need to look at details of the location and nature of the building to determine earthquake damage rather than relying on vibration maps, which he said are only useful for a broad situational awareness perspective and are intended to be used on a scale of at least 20 kilometres.

Professor Quigley said: “Insurers are looking at very rudimentary models that show the intensity of the shaking area and then saying that the intensity of the earthquake shaking in that area was not strong enough to cause damage.”

“Geoscience Australia, which is one of the lead custodians of that data, specifically has information that says you can’t do that.”

[ad_2]