By Eugene Bingham
Tsunami experts believe a bomb secretly tested off the coast of Auckland 50 years ago could be developed to devastating effect.
University of Waikato researchers believe a modern approach to the wartime idea tested off Whangaparaoa could produce waves up to 30m high.
Dr Willem de Lange, of the Department of Earth Sciences, said studies proved that while a single explosion was not necessarily effective, a series of explosions could have a significant impact.
"It's a bit like sliding backwards and forwards in a bath - the waves grow higher," Dr de Lange said yesterday.
He was responding to a Weekend Herald report of experiments at Whangaparaoa in 1944-45 to create a tidal wave bomb. The top-secret work by the late Professor Tom Leech was detailed in 53-year-old papers released by the Ministry of Foreign Affairs and Trade.
Dr de Lange said a coastal marine group from the university recently studied the likely impacts of underwater volcanic explosions.
Their work concluded that the next eruption in the Auckland region was likely to be under water, given the large amount of water around the city.
But tests showed a single explosion in the Hauraki Gulf would not trigger much of a tsunami.
"For most places the wave was less than 1m high, but it could be a bit more in the Tamaki Estuary."
Dr de Lange said the waves were not high because the energy was projected upwards, not sideways. He believed the same principle would be true for a tsunami bomb.
"You can't confine the energy. Once the explosion gets big enough, all of its energy goes into the atmosphere and not into the water. But one of the things we discovered was if you had a series of explosions in the same place, it's much more effective and can produce much bigger waves."