Kaikōura rocked by more earthquakes in 2018 than any other region

Following the destructive 2016 Kaikōura earthquake, the South Island region was rocked by the most earthquakes of anywhere in New Zealand in 2018.

Data from GNS Science shows that the region had roughly 3000 earthquakes in 2018, which seismologist Sam Taylor-Offord puts down to the large number of aftershocks occurring after the 7.8-magnitude earthquake in 2016.

Mr Taylor-Offord said the aftershocks are a part of a "sequence", common after large quakes and which can continue for many years. For example, he says only now - about eight years later - is the aftershock sequence caused by the major Christchurch earthquakes of 2010 and 2011 "calming down".

He said it was difficult to pinpoint an average magnitude of quakes which hit the Kaikōura region, as many were so small they may overwhelmingly sway the average and provide a disingenuous result.

Other volatile areas in 2018 include around Te Araroa near the East Cape, which was rocked by its own massive earthquake in 2016, and Fiordland.

The volatility of the Fiordland region is normal, as the boundaries of the Pacific Plate and Australian Plate run from Fiordland along the Alpine Fault, before heading out east near Wellington and up past East Cape.

"This plate interface is so volatile seismically because the plates are colliding along a narrow strip... at a great speed, geologically speaking," said Mr Taylor-Offord.

Movement on several fault lines around the Kaikōura region contributed to the massive 2016 quake, which ripped open large chunks of land in the region; destroyed homes, roads and railways; and was ultimately responsible for the deaths of two people.

Although other areas were far quieter in terms of the number of earthquakes registered, Mr Taylor-Offord said "any part of New Zealand could experience a damaging earthquake at any time in the future".

"All New Zealanders need to be prepared in the event of a damaging earthquake."

There were a swarm of earthquakes off the coast of Northland late in 2018 and early this year, which confused seismologists because Northland has one of the lowest rates of seismic activity in New Zealand. Of 19,508 earthquakes last year, only 32 occurred in the region.


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