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.
