Risk from earthquakes ‘too easily forgotten’

Press, 7 January 1987, Page 3

Risk from earthquakes ‘too easily forgotten’

PA Wellington New Zealand had so few strong earthquakes last year that people are in danger of forgetting the normal level of risk, says a geophysicist, Dr Warwick Smith. The superintendent of the nation’s seismological observatory, Dr Smith said the largest shallow earthquakes that occurred reached only magnitude 5: on February 13 in the Hastings area, on July 11 to the south of Fiordland, on July 12 to the southeast of Arthur’s Pass, on September 18 near Lake Pukaki, on October 10 in southern Hawke’s Bay, and on November 28 near Arthur’s Pass. Some of these were felt quite sharply, such as the one which shook Hokitika. Others were far enough away from large population centres that they did not cause much concern, such as the July 12 shock which, at magnitude .5.4, could have caused dam-

age but was apparently felt only slightly in Christchurch and just barely in Dunedin. The October 10 shock was felt strongly in Palmerston North, and slightly in Napier, said Dr Smith. The Seismological Observatory’s files were full of recordings of small earthquakes felt at a few places, but which caused no significant damage. The most important of these was the earthquake on November 13 which was reported as “the biggest to hit the capital in years.” It was actually of magnitude 3.9, but was centred less than 20km away and so was felt quite sharply. There were reports of Wellington buildings swaying, and of people alarmed, but the instruments at Kelburn indicated that the ground there only moved about Imm. “Here, then, is the quandary of the seismolo-

gist, how to convey the information that this was really a very small earthquake, and that a magnitude 6 shock, still only moderate, would be about a thousand times as large as this, without giving the impression of crying wolf,” Dr Smith said.

Sometimes large earthquakes which affected other people helped to make the point.