New Zealand Scientists have discovered a faultline beneath Cook Strait is much longer than previously thought and will increase the earthquake and tsunami risk to central New Zealand, New Zealand Press Association reported Monday.

The 70-km-long "Boo Boo Fault" was mapped using high-precision sounding equipment by researchers aboard the National Institute for Water and Atmospheric Research (Niwa) vessel Tangaroa, scientist Philip Barnes of Niwa was quoted as saying.

"It's probably the most exciting thing we've seen so far in the southern Cook Strait area," Dr Barnes said.

The fault line runs roughly east to west between Cape Campbell, on the eastern tip of the upper South Island, and Cape Palliser, the most southerly tip of the North Island, about 50km offshore of Wellington.

While scientists knew it existed they were unaware the faultline, estimated to be no more than 500,000 years old, was so long. "It's a large fault, it's a long fault, and it's got a high slip rate, so it's an important fault in terms of the plate boundary zone," Dr Barnes said.

Lead scientist in seismic hazard modelling at the Institute of Geological and Nuclear Sciences, Mark Stirling, said the discovery was "significant" and would increase Wellington's earthquake and tsunami risk.

While precise calculations were yet to be made, it was likely the Boo Boo Fault would increase the return rate for a "strong shake" in Wellington from a one in 15-year event to about once every 10 years, he said.

But although the new faultline was more active than the notorious Wellington fault, which ran through the city to the Huttvalley, its distance offshore reduced the risk it posed to life and property.

There was a "subtle but significant" increased risk of tsunami for the city and coastal Marlborough, Stirling said.

Scientists would adjust the national seismic risk model in light of the new fault and others picked up by the Niwa surveys.

Dr Barnes said the multi-beam sounding equipment had allowed scientists to accurately plumb deep-sea canyons, yielding startling images of the sea floor.

In that sense, it was a breakthrough and an exciting find.

The faultline was named after the Boo Boo stream near Cape Campbell.

Source: Xinhua