2 Jan 2017

A year of shocks - 2016 breaks NZ quakes record

9:54 am on 2 January 2017

A total 32,800 earthquakes were recorded in New Zealand in 2016 - the most ever in a calendar year.

Seismograph

A seismograph on display in the GeoNet briefing room. Photo: RNZ / Alison Ballance

GNS seismologist John Ristau said 2011, the year that the deadly magnitude 6.3 shake hit Christchurch, held New Zealand's previous record for the most earthquakes.

"That was our previous record of 29,000 earthquakes that we located that year, but maybe actually if we took a 12-month span beginning December 2010 - when the Darfield earthquake happened and then the 12 months after that - that 12-month span may have actually been higher."

GeoNet said two quakes of magnitude 7 or higher - and the resulting aftershocks - were the main contributors to the geologically busy year.

A magnitude 7.1 quake off the East Cape in September, which triggered a small tsunami, was widely felt around the North Island but there was minimal damage on land.

GeoNet said that in any other year, it would have been the biggest quake to hit New Zealand.

But then a magnitude 7.8 quake struck near Kaikōura in November, causing extensive damage to property, lifting the seabed and rupturing the coastline.

Thousands of aftershocks were felt in the days afterwards.

GeoNet said that on average it recorded about 20,000 earthquakes a year.

GeoNet recorded one volcanic eruption, on White Island.

The moderate steam and gas-driven eruption in April ejected the Crater Lake, created a new sub-crater, generated landslides and caused collapses, and excavated about 13 metres of the Crater Lake floor.

Parts of the volcano were left covered in green-tinged ash.

Meanwhile, Mt Ruapehu's Crater Lake went through cycles of heating and cooling, and geysers in Rotorua that had been quiet for 15 years decided to reawaken.

BY THE NUMBERS

* 32,800 quakes recorded

* Two quakes magnitude 7 or higher

* 2019 quakes magnitude 4 or higher

* More than 80,000 landslides

* Two tsunamis

* One volcanic eruption

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