Alpine Fault earthquake could isolate West Coast for six weeks

The Alpine Fault runs across the South Island.

The Alpine Fault runs across the South Island.

An Alpine Fault earthquake could isolate thousands of people on the West Coast for six weeks, a geologist says. 

It would knock out highways and railway lines connecting the coast to the rest of the South Island, some of which could take more than six months to restore.

University of Canterbury geologist Dr Tom Robinson said post-earthquake recovery would need to focus on restoring those lifelines. .

The key work would be restoring Arthur's, Lewis and Haast passes and the rail line, he said. 

The Lewis Pass could be restored in about six weeks.

Based on the extent of landsliding expected, Arthur's and Haast passes and the rail line could take more than six months to restore, he said. 

Robinson, who has just graduated with a PhD in geology, said the effects of earthquakes were not limited to the ground shaking.

There would be liquefaction like that experienced in the Christchurch quakes. 

Earthquakes on the Alpine Fault are thought to produce widespread landslides throughout the South Island.

Robinson said that would particularly affect sections of West Coast highway, including State Highway 6 between Hokitika and Wanaka.

A route from Hokitika to Nelson, via Greymouth and Reefton, was expected to have limited landsliding, "and is therefore considered the most critical link in the network", he said. 

"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."

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"Planning for these effects can substantially improve our understanding of earthquake hazard," he said.

He recommended that section of road was suitably reinforced and that Nelson and Blenheim were used as primary staging posts for emergency responders.

That would leave Christchurch and Dunedin, which were not expected to be badly affected, to focus on the response for badly-affected areas in inland Canterbury and Otago. 

 - Stuff

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