Nelson heads earthquake risk list

Press, 11 October 1985, Page 2

Nelson heads earthquake risk list

PA Wellington The city of Nelson has a 25 per cent chance in 50 years of experiencing an earthquake of similar intensity to the recent Mexico earthquakes, said the Minister of Science and Technology, Mr Tizard, yesterday. He told Parliament in response to a question that the corresponding 50-year probability per centage level (in comparison with Mexico) for Palmerston North was 24; for Wellington, 23; Wanganui, 19; New Plymouth, 13; Napier, 12; Greymouth, 12; Christchurch, eight; and Rotorua, five.

“The city of greatest risk is clearly Wellington, not because earthquakes are any more likely to occur there than anywhere else in the centre of the country but because it is a large

centre of population,” Mr Tizard said. He said seismologists used the term “intensity’’ to describe the severity of ground motion and in any one earthquake the intensity varied from place to place. “In the case of Mexico City the intensity was high because the city is founded on a dry lake bed rather than on solid rock,” Mr Tizard said. He said the destructive power of an earthquake was determined not by its magnitude but by its intensity in large centres of population. “The results of the most recent study by the D.S.I.R. can be expressed as the probability that particular locations would be subjected to an intensity as was experienced in Mexico City during any 50 year period,” Mr Tizard said.