Strong Milford Sound earthquake wasn't on Alpine Fault - seismologist

The earthquake struck on Monday night.
The earthquake struck on Monday night. Photo credit: GeoNet and Getty

GNS Science says Monday night's widely felt earthquake in Fiordland was typical for the region, and not on the Alpine Fault.

The 5.5 magnitude earthquake hit at a depth of 12km at 10:35pm on Monday night, roughly 15km north of Milford Sound in the South Island.

Nearly 7000 people reported feeling it, but seismologist John Ristau said it was minor compared to an Alpine Fault quake.

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 said in June that 30 percent was still the current probability.

"Roughly this [Monday's] earthquake is about 1000 times smaller than what an Alpine Fault earthquake would be," Ristau told Newshub on Tuesday.

He said the strongest message is that quakes can happen at any time, with no way to predict when or where.

"Especially if you are living or in one of the more active areas of New Zealand, such as along the West Coast of the South Island.

"We should always be aware, and always be prepared."

Emergency Management Southland said it had no reports of any major damage or injuries following Monday night's earthquake.

It was originally reported by GeoNet to be a magnitude 6.2 but this was revised down.

The quake was followed by at least 10 aftershocks, which GeoNet said was normal for this size earthquake.