Locals turned out in their dozens to rescue paua thrust out of the ocean following 2016's Kaikoura Earthquake. Nineteen months on, some habitats are still struggling. Photo / File
Locals turned out in their dozens to rescue paua thrust out of the ocean following 2016's Kaikoura Earthquake. Nineteen months on, some habitats are still struggling. Photo / File
The contortion of Kaikoura's coastline in 2016's big quake was the most variable observed anywhere in the world in modern times, scientists say.
Nineteen months after the 7.8 event, researchers have shared a range of dramatic new insights into its impacts on Kaikoura's world-renowned environment and local sealife.
Along with setting off more than a dozen faults and triggering more than 10,000 landslides, the November 14 midnight shake pushed around 110km of coastline as high as 6.5m upward, and as far as 2.5m downward.
GNS Science earthquake geologist Dr Kate Clark and colleagues measured the coastal deformation using a combination of field surveying, satellite measurements and high-resolution topographic surveys undertaken before and after the event.
About three quarters of the coastal stretch between Haumuri Bluff and Cape Campbell underwent uplift - nearly half of it involving the land being thrust up higher than a metre.
Around a quarter of that stretch underwent a minor amount of subsidised, and only a localised area nearby the Kekerengu fault slipped down by more than a metre.
Clark said just 3km of coastline, around Peketa, was left unchanged by the event, and the entire Kaikoura Peninsula and much of the coastline north and south of it was uplifted by between 80cm and one metre.
"Uplift of the peninsula and the surrounding area is attributed to an entirely offshore fault called the Kaikoura Peninsula fault," Clark said.
"Two strands of the Papatea fault cross the coastline at Waipapa Bay and between these faults the land was uplifted five to six metres, creating a new rocky coastal platform extending 200 to 300m offshore from the pre-earthquake coastline."
It wasn't the first time the landscape had been warped by big quakes.
Evidence of previous big quake-driven uplifts was preserved by uplifted beaches, also called marine terraces, which fringed many parts of the coastline from Oaro to Cape Campbell.
"These marine terraces are the subject of ongoing studies at GNS Science as we seek to understand how often large earthquake like the 2016 earthquake occur."
Other research presented this morning described impacts on marine species.
About three quarters of the coastal stretch between Haumuri Bluff and Cape Campbell underwent uplift - nearly half of it involving the land being thrust up higher than a metre. Photo / File
Sampling since the event had shown massive losses of habitat-dominating large brown algae, red algae and invertebrates such as paua and grazing snails.
For several months after the quake, there was a bloom of sea lettuce in the mid and lower tidal zones along most of the coastline from Omihi to Cape Campbell, as a result those losses and masses of fine sediments from crumbling rocks.
In some places where tidal inundation still happened, such as at Kaikoura and Cape Campbell, the water was shallow, immersion times were short, and temperatures could reach lethal levels for species within them.
Sediments were also still clouding nearshore waters in many areas, reducing the amount of food available for small invertebrates and other species.
While large numbers of paua were seen in fished areas that were less affected by the uplift, there had been little to no recovery in some other harder-hit habitats.
There was no observed impact on lobsters, blue cod and Hector's dolphins, although tonnes of sediment that was flushed through the Kaikoura Canyon likely prompted sperm whales to temporarily shift away.
All of the studies were part of a $2m research programme focused on tracking the recovery of Kaikoura's marine species.
"The research has given us a good baseline to measure how the recovery is progressing and where we need to focus our attention in the future," Ministry for Primary Industries fisheries science manager Richard Ford said.
"Continued monitoring of the recovery progress will inform future marine management options for when and how the current closure of shellfish and seaweed fisheries may be lifted."
