Seismologist Warns of Megathrust Earthquake Threat for New Zealand

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Author: Patrick O' Sullivan

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Less than 100km off the coast of Hawke’s Bay is a deep-water trench that could be the site of a potential megathrust earthquake similar to the 2011 Japan earthquake, says seismologist Kevin Furlong.

Despite the Hikurangi Trench’s potential, he said very little was known about the underwater valley, where the Pacific plate was dragged underneath the Australian plate.

Professor Furlong, of Pennsylvania State University, said the worst-case scenario for the East Coast was not yet known.

“Many, if not most, scientists working on these megathrust earthquake plate boundaries would argue that, although it is very, very unlikely, until we can demonstrate otherwise we should expect that major segments of these boundaries could rupture simultaneously.

“Most of the time, as was the case in Japan for the past several hundred years at least, segments rupture individually and so maximum earthquakes are in the mid-to high magnitude 7 range. But on rare occasions, such as in 2011 in Japan, bigger ruptures can occur.

“We need to decide how best to manage that potential and uncertainty.”

The trench will soon be part of a global study into megathrust earthquakes.

“Although we understand the general concept and general physics of megathrusts – the big subduction zone earthquakes – we are finding in our data from recent major events such as in Sumatra [Boxing Day 2004], Chile in 2010, and most recently in Japan, that they each have characteristics that differ from each other, and our existing models of how we might think they should behave during the actual earthquake rupture are incomplete,” he said.

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