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article imageNew Zealand's Kaikoura earthquake was the most complex ever

By Tim Sandle     Mar 23, 2017 in Science
The large earthquake that struck New Zealand in 2016 has been declared the most complex earthquake ever, according to scientists. This has implications for how earthquakes are monitored and responded to in the future.
The Kaikoura earthquake, which struck New Zealand in November 2016, had a magnitude 7.8 (Mw), with the focus on the South Island. The quake occurred two minutes after midnight (local time) on November 14 (11:02 on November, 13 Coordinated Universal Time). The earthquake started some 15 kilometres (9 miles) north-east of Culverden and 60 kilometres (37 miles) south-west of the town of Kaikoura. The tremors began at a depth of some 15 kilometres (9 miles). The ruptures (cumulative magnitude of 7.8) occurred on multiple fault lines in a complex sequence that went on for two minutes. A tsunami warning for the eastern coasts of the North and South Islands and the Chatham Islands was issued and a wave of 2.5 meters (8.2 feet) was recorded.
This was the second largest earthquake, in terms of magnitude, to hit New Zealand since records began. Such was the scale of the quake that $900 million insurance claims were made. In terms of human cost, several casualties were recorded.
In the aftermath of the earthquake scientists have declared the earthquake to be the most complex yet observed. Research has revealed at least 12 separate faults breaking during the quake. The review also established that scientists would never, based on previous knowledge, have predicted such an earthquake. With is Dr. Ian Hamling from the New Zealand's geophysics research agency (GNS Science) told the BBC: "What we saw was a scenario that would never have been included in our seismic hazard models."
Key to the complexity is the revelation that the Kaikoura earthquake shunted parts of the South Island more than 5 meters closer to the North Island. This rupture is described, in the resultant research paper, as highly unusual, according to the New Zealand website Stuff. This particular rupture has challenged the scientific consensus because scientists previously assumed faults more than 5 kilometers apart would not continue to rupture. It is thought some very large stress changes introduced early in the earthquake triggered the later segments to fail. The event has now caused a rethink in relating to predicting the course that earthquakes may take and the extent of damage they might cause.
The findings are explored more fully in the journal Science, with the research paper "Complex multifault rupture during the 2016 Mw 7.8 KaikĊura earthquake, New Zealand."
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