Nelson is sinking


Nelson sank up to 20mm after the Kaikoura earthquake says a GNS scientist, on top of the annual 2-3mm the region is normally sinking.

Wellington-based geodetic scientist Sigrun Hreinsdottir says that while people needn’t panic, it is something residents and local councils need to consider when thinking about long-term planning.

Sigrun says there are 200 recording stations throughout New Zealand run by LINZ and Geonet that continuously monitor land movement, including three in the Nelson region.

“The stations in Nelson showed a drop ranging from between 10-20mm after the Kaikoura earthquake. It’s not a huge change, but it is significant,” she says.

“But our monitoring has also shown that the Nelson region has been subsiding 2-3mm per year since we first started observing the area in 2004.

“This is something that is of huge interest to scientists, and it is important when we think about sea levels changing too.

“2-3mm a year may only sound like a little bit – but when you add on the sea level rise on top of that…”

A recently published paper by GNS Science shows that last November’s magnitude 7.8 earthquake raised up some parts of the South Island by eight metres.

It also shunted parts of it more than five metres closer to the North Island.

“It is just part of living on a tectonic boundary,” says Sigrun.

“Hopefully it will prompt local councils to think more about forward planning.”

A spokesperson from Nelson City Council said council had not seen the information and could not comment until it had a chance to properly consider it.