Tsunami Could Hit N.Z. Coast Without Warning

Press, Volume CVI, Issue 31225, 24 November 1966, Page 22

Tsunami Could Hit N.Z. Coast Without Warning

As there were practically no tidal stations between New Zealand and the South American coast, New Zealand could get no warning of a tsunami generated in the South Pacific until it hit the coast, the Director of Civil Defence (Brigadier R. C. Queree) told 120 delegates attending the fifth annual conference of civil defence controllers at Lincoln College. A tsunami, or seismic sea wave, was a gravity wave in water set in motion by underwater disturbances, usually an earthquake, said Brigadier Queree. It was frequently called a tidal wave although it had nothing to do with the tide. Tsunamis were generated mainly in ocean trenches around the Pacific, but they could be generated anywhere in the Pacific and there was no correlation or sequence between them. There was no way of predicting where or when the next seismic wave would be generated. At a depth of 30,000 ft, a tsunami travelled at 670 miles an hour and at 12,000 ft it travelled at 425 miles an hour, said Brigadier Queree. The speed was less in shallower water. The operation of the warning system began with the detection and location of major earthquakes occurring around the Pacific Ocean. Seismic waves travelling through the earth from major earthquakes triggered alarms on instruments at coastal and geodetic survey observatories located at Guam, Mariana Islands, Arizona, and Honolulu. These seismic readings were forwarded to Honolulu Observatory.

Honolulu Observatory staff determined the location and magnitude of the earthquake. If the earthquake was in a) favourable location for generating a tsunami and the mag-) nitude was large enough, the' observatory got in touch with i tide stations near the epi-i centre for information. A seismic wave generated) on the South American coast would take about 12 hours to) reach a point 600 nautical' miles from Wellington, said ■ Brigadier Queree. No warning' could be given if the wave were generated only an hour’s) travelling time from NewZealand. Even when there was a wanting there was very little; that could be done to protect; fixed property, said Brigadier; ) Queree. All that could be done ; was to see to the protection of lives. “Greatest Danger" The greatest danger all con-. trollers had to face in their; districts was waning interest, the civil defence officer for the Dunedin combined district (Mr D. Forsyth) said, when speaking on the essentials of a civil defence plan. “We enlist the services of a man, he gets an arm band, and then nothing happens for the next 12 months, so his interest flags,” said Mr Forsyth. Interest had to be maintained