An earthquake which hit north of Milford Sound has been felt by many across the South Island.
Geonet records the quake as a 4.7 magnitude shake, which struck at a depth of 5km at about 10:07am on Tuesday.
It was initially described by Geonet as "strong" before being downgraded to "moderate".
Within seconds, people across the South Island were saying they felt the quake, including in Dunedin and Christchurch. Most labelled it "weak" or "light" in strength.
It's unknown if the quake hit on the nearby Alpine Fault.
The last time the Alpine Fault had a major rupture was in 1717, when a magnitude 8.1 earthquake hit the South Island.
In 2012, research from GNS Science said there was a 30 percent chance a large, magnitude 8 quake will occur in the next 50 years on the fault.
GNS Science says a large rupture on the fault would "produce one of the biggest earthquakes since European settlement of New Zealand".
That prediction first came after scientists studied an 8000 year-long record of 24 Alpine Fault earthquakes based on data gathered near Lake McKerrow, northeast of Milford Sound.
It found that the average time between large earthquakes was 330 years - although some historical quakes studied did have intervals in the range of 140-510 years.
Geologists say you generally can't predict whether a big quake is about to happen based on smaller foreshocks - while many large quakes are preceded by smaller ones, just as many aren't.
Nor do small shocks reduce the chance of a big one happening - they're just not strong enough to release the tension.
Newshub.
