South Island moves closer
The Kaikoura quake ruptured several faults in the area including near Waiau.
The deadly 7.8 Kaikoura quake was so powerful, parts of the South Island are now six metres closer to the North Island, new research has revealed.
A study led by GNS Science is today being published in the prestigious journal Science.
It analyses the Kaikoura quake, which struck just after midnight on November 14, in unprecedented detail, thanks to it being one of the bestrecorded large earthquakes anywhere in the world.
Researchers analysed a wide range of quake data including satellite radar imagery, field observations, GPS data and coastal uplift data.
Scientists said the results might force a rethink of the way they look at earthquake hazards along plate boundary zones across the world, due to the complex and unusual patterns in the quake.
Their study shows the shaking was so violent, parts of the South Island were permanently shifted higher, and northwards.
From Kaikoura to Cape Campbell, the earth was pushed 6m closer to the North Island, as well as several metres higher in various places.
Near the Papatea Fault, the ground was raised as much as 8m.
Despite the major movement, scientists believe it would have hap- pened almost simultaneously with the earthquake.
The earthquake ruptured along a record 21 faultlines. At least 12 major crustal faults were involved, as well as nine lesser faults.
Some of the faults involved were previously unknown to scientists.
The total rupture travelled 180km but only took two minutes to travel its entire length.
The Kekerengu Fault had some of the biggest movements, with deep pieces of the Earth’s crust shifting up to 25m at a depth of around 15km.
At the surface, the biggest movement was a 12m horizontal shift.
The authors of the study said the earthquake was so complex, it defied many of their conventional assumptions, including the degree to which an earthquake is controlled by an individual fault.
They said a rethink was now needed for how these issues would affect seismic hazard models around the world. Wellington Kaikoura The length of arrows shows proportional horizontal ground movement. The coloured background shows vertical movement.
Lead author and GNS Science geodesy specialist Ian Hamling said the quake was so long and complex it made it difficult to accurately pin down the magnitude.
This raised problems for earthquake early warning systems, and showed standard hazard models were too simple and restrictive.
“Scientists have known for a long time that this region is capable of producing complex earthquakes.
“Even so, the high level of complexity of the Kaikoura earthquake took many by surprise.
“It serves to underline why some scientists regard this region as the most complex plate boundary zone in the world.”
Hamling said the research would now continue, with a particular focus on any deformation as the ground continued to slip and adjust.
Even though the research was focused on a complex area, the insights are expected to help with understanding similar plate boundary zones around the world. See Felicity Jones, Fan Bing Bing, and more in Viva’s celebrity looks of the week. previews the weekend of Super Rugby after 8am with Justin Marshall. Rotorua’s Toastmaster joins Mike to warm up his vocal cords for a world record speech attempt.