Northland 'safest part of NZ for quakes'

As Canterbury struggles in the aftermath of Saturday's destructive earthquake, Northlanders can rest assured they live in possibly the most stable part of the country with little chance of a big quake hitting the region.
The earthquake measured 7.1 on the Richter scale, causing widescale damage, but no loss of life, when it rumbled through Canterbury early on Saturday.
But geologist Steve Edbrooke said Northland, with no known active seismic faults, had the lowest earthquake risk in the country.
"The records show that while there have been a number of earthquakes felt [in Northland], none of them were greater than 5 [on the Richter scale] and have all been pretty small," Mr Edbrooke said.
"And a lot of the earthquakes felt in Northland have been centred well away from the region. So you might get a bit of a shake from an earthquake in the Bay of Plenty, for instance, but for actual earthquakes centred in the region, they are pretty rare and pretty small."
He said with no active faults in Northland it was very unlikely there would be any hidden fault lines, as has been discovered in Canterbury from this quake.
"It's a pretty remote chance [of hidden fault lines]. There are lots of active faults in the Canterbury region, but this one was one we didn't know about," Mr Edbrooke said.
"But with them having quite a few [faults] it was no huge surprise to find this one. In Northland there are no active faults so we wouldn't expect to find any hidden ones."
A geological map, compiled from a GNS Science survey earlier this year, shows Northland to be possibly the most stable region in the country.
The GNS survey and map also shows that Northland is made up of displaced rocks that have been broken and fractured during their 22-million year journey, making them relatively weak.
That, Mr Edbrooke said, explained why erosion and landslides, after intense rainfall, were the dominant natural hazards in Northland. He said unknown seismic activity about 22 million years ago had placed the rocks that formed Northland on the seafloor about 100km northeast of Whangarei. The rocks had then been progressively shunted southwest by tectonic forces.
The region had no historical records of large earthquakes and no known active faults. "Because of this, the risk of locally generated tsunami is also low, but the [Northland] east coast in particular is vulnerable to tsunami generated by distant earthquakes and submarine volcanic eruptions."