Undersea fault line risk swells

STACEY KIRK
Last updated 15:52 14/11/2012

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Seismic research off the coast of New Zealand has identified another 200 fault lines that could cause catastrophic tsunamis if a significant earthquake struck.

GNS Science, along with the National Institute for Water and Atmospheric Research (Niwa), have just wrapped up a major project to revise the New Zealand National Seismic Hazard Model (NSHM).

A number of newly identified faults have now been added to the model, raising the total number of known fault lines by about 200 - to nearly 530.

Niwa said a particularly large fault found offshore near Canterbury had the potential to cause a significant tsunami.

The large fault was found in the bedrock under Pegasus Bay shortly after the February Christchurch quake when GNS Science and Niwa conducted a survey of 800 square kilometres.

Scientist Philip Barnes said New Zealand had to prepare for marine quakes in many locations.

"There are many earthquake faults on the sea-floor around our coasts, and the next major earthquake could be centred offshore. So it highlights the need for coastal marine investigations of active earthquake faulting, for both ground-shaking hazards and tsunamis,” he said.

"Niwa's geosciences team responded rapidly to the Canterbury earthquakes, working closely with the Natural Hazards Research Platform and other authorities to inform the recovery.”

In the last decade there have been tens of thousands of marine shakes, some easily felt and some hardly registering.

Two of the most devastating earthquakes in the past 10 years were not so because of the shaking, but rather the tsunamis which came after.

The 9.1 magnitude quake which struck the northeast coast of Japan last year generated a massive wave with up to 40 metres of run-up height, Barnes said.

Such a wave was not out of the realms of possibility here and the information for a number of regions had been updated with the latest finds.

“We also now have some experience in how to respond and learn more about the cause of a major earthquake if such an event occurs. The more background information we have on active faults, the better.”

Barnes would be presenting some of the information at the New Zealand Coastal Society Annual Conference which is being held over the next two days.

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