New Zealand’s north and south islands are moving closer together after 7.8-magnitude earthquake

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New Zealand’s north and south islands are moving closer together after devastating 7.8-magnitude earthquake in 2016

  • Kaikōura earthquake brought the two islands five metres closer together in 2016
  • Post-quake monitoring revealed this movement is still ongoing in New Zealand
  • Cape Cambell on the coast of South Island 35 centimetres closer to Wellington

New Zealand‘s north and south islands are ‘creeping’ closer together in the aftermath of the devastating Kaikōura earthquake.

The 7.8-magnitude earthquake initially brought the islands five metres closer when it struck the tip of South Island in November 2016.

Now two years on, post-quake monitoring has revealed the land is still reshaping due to unsettled fault lines – with Cook Strait, the body of water between the two islands, narrowing.

The 7.8-magnitude earthquake initially brought the islands five metres closer when it struck the tip of South Island in November 2016 (file photo)

The 7.8-magnitude earthquake initially brought the islands five metres closer when it struck the tip of South Island in November 2016 (file photo)

The northern part of South Island has been moving northeast towards its sister island since the quake, GNS Science revealed. 

Dr Sigrún Hreinsdóttir​, a GNS Science geodetic scientist, told Stuff that Cape Campbell on the northeastern coast of the South Island is now 35 centimetres closer to Wellington.

Dr Hreinsdóttir also said GPS monitoring stations installed after the earthquake showed Kaikōura had moved 15 centimetres east, Blenheim had slipped 15 centimetres northeast and Nelson had moved five centimetres southeast.

The country’s capital, Wellington, had also moved five centimetres to the northeast.

But the scientist said it was difficult to work out which fault line was responsible for each movement.

She said: ‘In reality we are having all these creepings going on and the question is, which is the dominant factor? 

Now two years on, post-quake monitoring has revealed the land is still reshaping due to unsettled fault lines (file photo)

Now two years on, post-quake monitoring has revealed the land is still reshaping due to unsettled fault lines (file photo)

‘The idea there was a quite significant component on that plate interface was the surprising thing to us.’

Dr Hreinsdóttir said the land creep is likely to continue for years at a much slower pace.

The Kaikōura earthquake tore apart a record of 25 faults when it hit near to North Canterbury, on the tip of South Island.

It claimed the lives of two and caused dozens of injuries as parts of the Malborough coast were lifted more than six metres in some places and fell more than two metres in others. 

HOW ARE EARTHQUAKES MEASURED?

The magnitude of an earthquake differs from its intensity.

The magnitude of an earthquake refers to the measurement of energy released where the earthquake originated.

Magnitude is calculated based on measurements on seismographs.

The intensity of an earthquake refers to how strong the shaking that is produced by the sensation is.

A 5.3 magnitude earthquake hit the Channel Islands off the coast of southern California on Thursday at 10.30am

A 5.3 magnitude earthquake hit the Channel Islands off the coast of southern California on Thursday at 10.30am

According to the United States Geological Survey, ‘intensity is determined from the effects on people, human structures and the natural environment’.

Earthquakes originate below the surface of the earth in a region called the hypocenter. 

During an earthquake, one part of a seismograph remains stationary and one part moves with the earth’s surface.

The earthquake is then measured by the difference in the positions of the still and moving parts of the seismograph. 

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