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Judi Lynn

(160,219 posts)
Tue Nov 27, 2018, 09:37 PM Nov 2018

New Zealand's Islands Are Creeping Closer Together


By Stephanie Pappas, Live Science Contributor | November 27, 2018 10:02am ET

- click for image -

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An aerial view of Wellington, New Zealand. A new study shows that the 2016 Kaikoura quake pushed Cape Campbell, on the northern end of the South Island, nearly 14 inches (35 centimeters) closer to the city of Wellington, which sits just across the Cook Strait on the North Island.
Credit: Shutterstock



In the two years since a magnitude-7.8 earthquake rocked New Zealand, the country's South Island has slid a smidgeon closer to its North Island.

As the Earth's crust continues to shift after its cataclysmic rupture during the 2016 Kaikoura earthquake, Cape Campbell on the northern side of the South Island has shifted nearly 14 inches (35 centimeters) closer to the city of Wellington, which sits across the Cook Strait on the North Island, said Sigrún Hreinsdóttir, a geodetic scientist at GNS Science, a research consultancy service in New Zealand.

The movement is too slow and subtle to be felt by humans, Hreinsdóttir told Live Science, but she and her colleagues have been measuring it with a combination of GPS sensors and satellite measurements. These measurements reveal that New Zealand is still feeling the effects of the 2016 quake, which killed two people when it struck just after midnight on Nov. 14. The measurements will also help scientists predict what size earthquakes New Zealanders could expect to face in the future, Hreinsdóttir said. [The 10 Biggest Earthquakes in History]

Complex crust
The Kaikoura quake was mind-bogglingly complex. It hit in a transition zone between two very different geologic regions, Hreinsdóttir said. In general, the country sits right on the edge of a subduction zone, where the Pacific plate grinds under the Indian-Australian plate. The border of this subduction zone runs along the east coast of the North Island. Meanwhile, the South Island hosts a strike-slip fault known as the Alpine Fault, where pieces of crust move horizontally in relation to one another. When the Kaikoura quake hitnear the South Island town of the same name, it ruptured more than two dozen fault lines in the area. One major question, Hreinsdóttir said, is how much of the resulting movement was due to those fairly shallow faults, and how much could be traced back to deeper subduction-zone faults far deeper in the crust.

More:
https://www.livescience.com/64175-earthquake-pushed-new-zealand-islands-closer.html
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