Alpine fault rupture will be ‘largest earthquake in recorded history’

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When the Alpine Rift ruptures, Timaru may shake for at least two minutes, but no widespread devastation is expected in the area, the councilors have been told.

Speaking to Timaru County Council’s Environmental Services Committee on Tuesday morning, Dr Tom Robinson, a senior lecturer from the University of Canterbury on the Disaster Risk and Resilience team, demonstrated modeling in the event of a failure – which could happen at any time.

While the standoff presentation showed that the shaking was expected to be “significant” with “significant damage” in the area, Robinson said the good news was that, since Timaru is so far from the fault, “it will not be the focus of the Alpine fault event.”

“The chimneys will collapse, there will be liquefaction around Washdiki and damage, but we will not see the same levels of damage that will occur on the West Coast,” he said at the meeting.

Read more: * Earthquake Roadshow: Prepare for when the big quake hits * High Alpine earthquake risk highlights need for preparation on West Coast * Alpine earthquake unlikely to cause tsunami in Timaru

Explaining the Pacific Ring of Fire and plate boundaries, Robinson said New Zealand is “tectonically incredibly complex”.

“We’re lucky in some ways – we’re one of only two places in the world where you can see the bug on the ground.”

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The Alpine Rift is expected to rupture within the next 50 years.

Robinson said research has shown that the last major earthquake on the Alpine Rift was in 1717. It is likely that the next major earthquake on the Alpine Rift will occur within “most of us or our children”‘s lifetime.

Over the past 8,000 years, he said, the fault has had 28 earthquakes, and there was no reason to suspect it would stop suddenly.

Patterns showed that the fault experienced a major earthquake on average every 300 years.

With this modeling, Robinson said, he was supposed to be ripped off in 2017.

This leads us to believe that there is a 75% chance of it exploding in the next 50 years. ”

He said that massive earthquakes that occurred in the fault in the past had a magnitude of 8.

“To put that in perspective, an 8-magnitude earthquake would be a vertical displacement, and the ground would move two to three meters.”

The intensity of the shaking damage will be at Modified New Zealand Intensity Scale (MM) 07, which means the entire South Island will feel it.

“MM5 and above would mean every New Zealander would feel the Alpine Rift rip.

“In Sydney they will feel it. This will be the biggest earthquake in recorded history.”

It would kind of shake “where you’re really, really scared” and desks would jump, and loose ceiling tiles would fall, he said.

The direction it ruptured was also important, Robinson said.

“We assumed that the epicenter would be somewhere around it [Aoraki] Mount Cook.

If it happened near Milford Sound it would be our worst case scenario. ”

He said this means that all of the quake’s energy will blast northward for about 400 metres.

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Monetization is expected at Washdyke. (file photo)

Council members were shown an animation showing how the earthquake spreads up the coast showing waves.

It showed Timaru shaking for at least two minutes after the earthquake started.

“There are two things we’re really concerned about — intensity and vibration,” said Robinson.

“Two minutes is a long time. A very, very long time.”

He said the earthquake would also create secondary hazards and could trigger landslides that could block the river and form an earthquake lake, causing increased spillage and channel erosion, and eventually could fail to cause a dam collapse flood.

Secondary risks are often much worse. ”

Robinson said roads across the South Island would be closed and there would be a loss of electricity.

However, Timaru should have fare and the east coast also has a “reasonably strong” net.

Chancellor Alan Booth asked if it was an advantage to build Timaru on basalt rock.

While this meant the chances of liquefaction were “very low,” Robinson said, the “bad news” was that rock solid meant the vibration would be felt more strongly.

“The shaking does not last long, but it will be stronger.”

In Ashdik, expect that there will be monetization.

Council team leader and emergency management advisor Phill Mackay said six Alpine Fault earthquake planning workshops had been held, and he expected a good framework for the work to be developed by the end of the year.

Chancellor Owen Jackson moved the Council to receive and note the data and seconded Booth.

All councilors were in favor of the statements.

John Bisset/Stuff

Built on basalt rocks, the earthquake is expected to be felt most powerfully in Timaru. (file photo)

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