Russia’s recent 8.8 magnitude earthquake in the Kamchatka region triggered tsunami alerts across the Pacific, including in Australia. No waves reached local shores but the event likely raised questions, particularly for local insurers and brokers in the property space, about how much risk the country faces from tsunamigenic earthquakes, or tsunamis generated by earthquakes.
“While the hazard from the frequency of tsunamigenic earthquakes is relatively stable over human timescales, Australia's risk is increasing,” said Alec Wild (pictured, left). “This is because our exposure is growing relentlessly, with more people, more valuable property and more critical infrastructure being developed in vulnerable, low-lying coastal areas.”
Wild is Aon’s senior catastrophe research analyst with its View of Risk Advisory group, Reinsurance Solutions. He said Aon’s national property database shows that 30% of properties are within 5km of the coast, with just over 10% within 1km of the coast. “This exposure is compounded by key economic assets such as ports, refineries, LNG plants, which are also often on or near the shoreline,” said Wild.
James Dalziel (pictured, right), WTW’s Earth Risk research lead at the Willis Research Network, said the main tsunami risk for Australia comes from “distance source events at large magnitudes” around the Pacific ring of fire and Indian Ocean.
“This could include locations like the Sunda Trench in Indonesia, the New Hebrides and Tonga Trenches in the Southwest Pacific and the Puysegur Trench south of New Zealand,” he said.
The Sunda Arc, for example, was the source of the 2004 Indian Ocean Boxing Day tsunami that generated waves with run up heights of up to 20 metres.
Wild added that the main threat to Australia comes from earthquakes occurring in these so-called subduction zones. He said the northwestern coast of WA is considered the most exposed to these tsunami risks due to its relative proximity.
“For example, the July 2006 tsunami, generated from an earthquake near Java, Indonesia, produced a 7.9m wave run-up height at Steep Point, WA,” he said. According to Geoscience Australia, this is the largest recorded tsunami to impact Australia in recent years.
The southern and eastern coastlines of Australia do also face some risk from tsunami threats. Wild said an earthquake in the Puysegur Trench is considered the most credible worst-case scenario for the densely populated and high exposure eastern seaboard, potentially generating dangerous waves with under two hours warning.
One factor that could strongly influence the country’s future tsunami risk is climate change. “Looking forward, sea-level rise compounds the hazard somewhat by allowing smaller tsunami waves to move further inland and by increasing the probability that a given tsunami height overtops existing coastal defences,” said Wild.
He cited a recent study on port networks that showed that the number of world ports suffering damaging inundation in a Manila-Trench-style tsunami could rise by 35% under end-century sea levels.
Wild said this tsunami risk trend is relevant to large Australian ports like Fremantle and Darwin. Dalziel agreed. “Effects such as rising sea levels may mean that subsequent tsunamis could have a greater potential impact on coastlines,” he said.
However, both brokers said that improved warning systems are helping to mitigate tsunami risks.
Wild said the Joint Australian Tsunami Warning Centre has “greatly increased” the capacity to mitigate casualties, through evacuations, and potential physical damage losses, through maritime advisories. “The insurance sector now has access to detailed models, such as the PTHA18, and advanced scenario tools and digital platforms that enable the mapping of portfolio exposures against detailed hazard footprints,” he said.
The Aon expert said this allows insurers and brokers to scenario-test the impact of plausible future tsunamis and advise clients on loss reduction strategies.
Dalziel said these warning systems “somewhat offset” the increasing risks by ensuring that preparedness and resilience measures can be put in place before a tsunami strikes – and that timely warnings are given when one is on its way.
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