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]
That matters, Hreinsdóttir said, because when a quake happens in a subduction zone, the amount of area that "breaks" determines the size of the shaking. If New Zealand's active subduction zone extends far south, it could mean that the country needs to prepare for especially large quakes.
So far, the researchers' data suggests that the deep, subduction-zone faults didn't make a big contribution to the Kaikoura quake right as it happened. But that deep interface does seem to be moving post-quake, Hreinsdóttir said.
The largest post-quake movements have already occurred, Hreinsdóttir said. Now, the earth is still creeping, but the movements are gradually tapering off. Following them into the future, though, will help researchers determine which movements come from the upper crust and which from deeper down. They'll also be able to figure out more about whether the quake put pressure on nearby faults, making a future quake more likely, or took some pressure off other faults, meaning the crust is likely to stay quiet.
"It's always important to monitor and measure what happens after an earthquake," Hreinsdóttir said.
7 Ways the Earth Changes in the Blink of an EyeImage Gallery: This Millennium's Destructive EarthquakesRare Footage of the Devastation of the 1906 San Francisco EarthquakeOriginally published on Live Science.