An Earthquake Moved New Zealand's North And South Islands About Five Meters Closer Together

The earthquake caused large cracks to appear in roads. NigelSpiers/Shutterstock

A huge earthquake two years ago is thought to have brought the two islands of New Zealand closer together, according to scientists.

Speaking to the New Zealand website Stuff last week, Dr Sigrún Hreinsdóttir from GNS Science said that the magnitude 7.8 Kaikōura earthquake on November 14, 2016, had brought the two islands about 5 meters (16.5 feet) closer together. Although the gap between them is still about 50 kilometers (30 miles), they’re getting closer now due to unsettled fault lines.

The quake is reported to have torn apart at least 25 faults, although it’s not clear which one has moved the islands closer. Since the quake, the gap has narrowed a further 35 centimeters (13.8 inches) from Cape Campbell in the south to Wellington in the north, while the city of Nelson on the South Island has also sunk a small amount, up to 20 millimeters (0.8 inches).

"In reality we are having all these creepings going on and the question is, which is the dominant factor?” said Dr Hreinsdóttir. “The idea there was a quite significant component on that plate interface was the surprising thing to us.”

The Kaikōura quake started in Waiau, North Canterbury, and moved towards Cook Strait. It is thought to have caused land to lift by more than 6 meters (20 feet) in some locations on the Marlborough coast and dropped by 2 meters (6.5 feet) elsewhere.

“The Kaikoura earthquake struck just after midnight and raced north from the middle of the South Island towards Cook Strait covering 170 kilometers [106 miles] in about 74 seconds,” said the AFP.

“New Zealand lies in the collision zone between the Indo-Australian and Pacific tectonic plates, part of the Pacific Basin Ring of Fire, and experiences more than 15,000 earthquakes a year although only 100-150 are strong enough to be felt.”

Speaking to The Guardian, GNS’s principal scientist Dr Kevin Berryman noted that it was “unusual that 25 faults ruptured simultaneously” during the earthquake.

“It’s fair to say that all earthquakes of magnitude 7.5 and above are invariably very complex,” Dr Berryman added. “We have to be prepared to live with a level of risk, but we should be asking how much risk is acceptable?”

According to GNS Science, the Kaikōura earthquake was “one of the most complex earthquakes” ever recorded in the world. The land is continuing to change even today, with rainfall, erosion, and human activity wearing down some of the changes.

“It is impressive to see areas that appear benign to us at a human timescale being completely reworked by the forces of nature,” they said.

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