A "silent earthquake" has just begun off the coast of Gisborne, and could take anywhere between a week and a month to unfold.
The quakes, otherwise known as slow slip events, can't be felt by humans or detected with a seismograph. They're recorded using plotted GPS stations with the fluctuating distance between the GPS stations giving an indication of the quake.
Over prolonged periods, their seemingly small movement can move faults the equivalent of a magnitude 5+ quake.
A silent earthquake's movement is plotted (GeoNet)
These slow-motion quakes were only discovered to happen in New Zealand in the early 2000s and there is still a lot to learn about them.
In fact, researchers from around the world are interested in these quakes because of the location of New Zealand in relation tectonic plates.
"There is worldwide interest in studying our subduction margin (where one plate dives beneath another). In terms of logistics, it's one of the easiest to study, as it's close to shore," GeoNet says.
And GeoNet's policy of making data freely available also adds to the appeal to international researchers.
"Japanese researchers from Kyoto and Tohoku Universities are currently out on a research vessel retrieving instruments that have been recording for a year, as well as installing more instrumentation to look at how the seafloor moves and deforms over time."