3 Oct 2019

Kaikōura faultline study shakes up earthquake science

10:06 am on 3 October 2019

New analysis of the 2016 Kaikōura quake could change the way scientists assess seismic hazards, with one of the faults proving more unusual than first thought.

Kaikoura earthquake - road damage

Road damage after the Kaikōura quake. GNS Science says that in complex earthquakes like Kaikōura's, the biggest hazard is from land displacement, rather than shaking. Photo: RNZ / Rebekah Parsons-King

In a study published in Science Advances journal this week, GNS Science researchers found the Papatea Fault, one of 24 in the region ruptured along 19km and shunted the earth upward by 8m in just a few seconds.

However, they found this fault did not build up stress in the usual way and instead seems to have been squeezed by other neighbouring moving faults.

Co-author and earthquake geologist at GNS Science Rob Langridge said the rupture stood out as one of the most dramatic elements of an unusual rupture sequence.

"It produced the largest vertical movements of all the faults that ruptured during the earthquake and it has puzzled scientists because its rupture could not be fitted to standard models of fault rupture," he said.

The paper, by two other GNS scientists along with University of Victoria (British Columbia) student Anna Diederichs and geophysicist Ed Nissen, used LIDAR - meaning light detection and ranging, an imaging method which detects distance - to examine the fault's unusual characteristics.

The ruptured faultline can be clearly seen on this Ward farm.

A ruptured faultline can be clearly seen on this Ward farm, where the fence was straight before the quake. Photo: RNZ / Tracy Neal

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