Alpine fault earthquake will involve more infrastructure challenges

A University of Canterbury geological sciences researcher says an alpine fault earthquake is likely to be markedly different to the Canterbury earthquakes, with infrastructure losses potentially exposing the regional economy rather than the concentrated building losses seen in Christchurch in 2010 and 2011.

Dr Tom Robinson, who has just graduated with his doctorate, says post-disaster recovery for an alpine fault earthquake will need to focus on rapid re-installation of critical lifelines in order to sustain the South Island economy.

“Long-term recovery will need to focus on re-instating critical lifelines connecting key economic production and tourism centres on the West Coast with the distribution centres in Christchurch and Dunedin.

“This will primarily require restoration of the Arthur’s, Lewis and Haast Passes as well as the railway line. Given the extent of landsliding anticipated, it is estimated that Lewis Pass will require at least six weeks to fully restore, while Arthur’s Pass, the rail line and Haast Pass could need more than six months.”

Dr Robinson’s PhD thesis was supervised by leading national hazard research experts at the University of Canterbury, Professor Tim Davies and Dr Tom Wilson.

Earthquake hazard is not simply strong ground shaking. It involves a series of complexly interlinked and cascading hazards that increase the impact of the event. Nowhere is this more evident than following the Canterbury earthquakes where liquefaction affected large swathes of the Christchurch’s eastern suburbs and elsewhere, leading to a complex and long-term disaster recovery.

“Planning for these effects can substantially improve our understanding of earthquake hazard and allow us to formulate and implement better emergency response and long-term recovery plans,” Dr Robinson says.

“Potentially one of the largest earthquake hazards facing New Zealand is the alpine fault. Earthquakes on this fault are thought to produce widespread landsliding throughout the Southern Alps, which has the potential to exacerbate the resulting disaster.

“This landsliding will present a major hazard to the critical infrastructure that passes through the Southern Alps, connecting the West Coast to Christchurch and the eastern South Island.

“The State Highway network is particularly exposed, with Lewis Pass, Arthur’s Pass, and SH6 between Hokitika and Wanaka all anticipated to be blocked by multiple large landslides.

“A route between Nelson and Hokitika via Inangahua, Reefton and Greymouth is identified as having limited exposure to landsliding, and is therefore considered the most critical link in the network.

“If bridges and other structures along this route can withstand the strong ground shaking they are exposed to, direct access to 30,000 people who would otherwise be completely isolated, will be possible.

“My study recommends ensuring this section of road is suitably reinforced and that the emergency response uses Nelson and Blenheim as primary staging posts for gaining road access to the West Coast Region via Inangahua and Reefton.

This will allow Christchurch and Dunedin, which are not expected to be badly affected, to be used as staging posts to focus response on badly-affected inland areas of Canterbury and Otago,” Dr Robinson says.

ENDS

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