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Earthquake shakes up risk complacency

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The partial collapse of a building front in Melbourne and shaking felt in several states following the Victorian earthquake is a warning against complacency about a risk for which Australians are generally unprepared.

Australia is not seismically active compared to New Zealand, Japan and the US West Coast, but the destructive 1989 Newcastle earthquake was a previous wake-up call about risks that do exist, with that disaster driving building code changes.

Countless buildings dating from before that time remain susceptible to ground shaking due to their construction type and the period when they were built. Double-brick structures are among the more vulnerable, research has shown, while many older buildings have features that may easily fall.

Risk Frontiers says the 5.9 magnitude Mansfield earthquake on September 22 was felt as far afield as Sydney, Dubbo, Launceston and Adelaide, all at least 700 km away.

In Victoria there were numerous reports of minor building damage and power outages affected parts of metropolitan Melbourne. The wall of Betty’s Burgers in Chapel St partly collapsed and residential apartments of up to 50 stories swayed for as much as 20 seconds, triggering panic among residents.

Smaller earthquakes have historically caused more damage in Australia than larger ones that have occurred in remote areas. Thirteen people died and 160 people were hospitalised after the 5.42 magnitude Newcastle earthquake. Some 50,000 buildings were damaged, including 40,000 homes. Insurance losses are estimated at $4.2 billion on a normalised basis.

Geoscience Australia Senior Seismologist Hadi Ghasemi and Australian National University Professor Phil Cummins say in an article on The Conversation that a 5.9 magnitude quake as far away as the Mansfield event shouldn’t cause significant damage to buildings that follow the current building code.

But cities and towns include countless buildings that don’t meet those standards and last month’s quake provided more than a hint of what could happen if there was a larger or closer event.

University of Canterbury Associate Professor of Environmental Science Ann Brower, who spent two months in hospital after she was the sole survivor of a bus crushed by falling bricks in Christchurch, says Victoria should prioritise fixes to non-structural unreinforced masonry.

Dr Brower’s advocacy in New Zealand led to a legislative amendment to hasten action to address and upgrade building features such as parapets, gables and chimneys.

“Earthquakes don’t kill people; buildings do. And those lovely decorative bits of buildings are the first to fall, even in relatively mild earthquakes like the ones Victoria gets from time to time,” she says in an article on The Conversation website.

“I am not saying all buildings in Victoria or Melbourne should be whizz-bang ‘earthquake-proof’ like those in Tokyo or San Francisco. I am recommending cheap, effective fixes to the bits of buildings that are easiest to fix, and deadliest if you don’t.”

University of Newcastle School of Architecture and Built Environment academics say in another article that, in addition to construction standards, national planning policy needs to take earthquake risks into account.

Adjunct Senior Lecturer Mark Maund, Discipline Head - Construction Management Kim Maund and Associate Professor Thayaparan Gajendran say improved planning will be even more important as population growth drives taller buildings and urban sprawl.

“With specific regard to earthquakes, we need to consider whether a particular location allows us to construct buildings that will be safe, provide safe access and escape via road and public transport, and allow for adequate evacuation centres,” they say.

“In earthquake-prone locations, we should consider the risk before approving tall buildings, those with large numbers of occupants, or those that cater for lots of people who are likely to need extra assistance in an emergency, such as hospitals, childcare and aged-care centres.”

Early claim lodgements after the Mansfield quake have largely reflected minor home building damage, such as fallen cornices and damage to plaster and render, rather than significant structural issues, the Insurance Council of Australia says.

Building inspections have revealed some cracking, and issues may emerge over time that were not obvious initially, but insurers have indicated they do not expect to incur major costs.

The timing of earthquakes can’t be predicted, and unlike many other natural disasters they are not associated with any “season” ahead of which preparations can be made, but the potential for sudden catastrophic damage is obvious.

The drive for building and planning reforms and improved disaster resilience in Australia has recently taken place amid a focus on cyclones, bushfires and flooding, especially in the context of climate change.

Latest events show earthquake exposures and ways to minimise risks should also not be forgotten.

The Conversation articles are available here, here and here.