Three ’Quake Zones ‘Absurd’

Press, Volume CV, Issue 31058, 13 May 1966, Page 12

Three ’Quake Zones ‘Absurd’

(New Zealand Press Association)

WELLINGTON, May 12. “It is simply absurd to zone New Zealand into three degrees of earthquake risk,” the superintendent of the Government Seismology Department (Dr. R. Adams) said today.

“New Zealand is a small country and should be decreed as one unit as far as earthquake risk is concerned,” he said.

Dr. Adams was commenting on a by-law recommending New Zealand be divided into three zones as far as structural engineering designs for earthquakes were concerned. The by-law was declared by a committee of the New Zealand Standards Institute, then the Standards Association, in December last year. Zone one, where the earthquake risk is greatest, runs through the “spine” of the country—from the Southern Alps, up through the Kaikouras and through the east coast of the North Island. The third zone, which is the least likely to experience an earthquake, takes in the area from Auckland northwards, and the Dunedin region. The rest of the country is included in zone two, in which the risk is not quite as great as in zone one.

An earthquake with a magnitude of 3.5-4 was recorded in Northland—the area with the least risk —early on Wednesday morning. The shock, which Dr. Adams described as “small,” was recorded at the Auckland

Museum and Whangarei seismology stations. Preliminary readings placed the epi-centre at Waipu. This is regarded as an “earthquake free” area. “There are about 200 shocks of this kind in New Zealand , every year,” Dr. Adams said. ; “No region can possibly be ’ described as ‘earthquake- . free’.”

A director of the Geophysical Division of the D.S.I.R. (Dr. F. F. Evison) agreed today with Dr. Adams that no area was free of earthquakes.

“New Zealand as a whole is a region of only moderate earthquake activity,” he said. “But on the evidence of past ’quakes in New Zealand and overseas, the highest standards in earthquake-resistant designs of buildings should be observed throughout the country.

“It is a great mistake to divide the country into three zones as far as building designs for earthquake risk are concerned,” he said. “We can learn a lot from sequences of 'quakes overseas recently. “First, the destructive earthquake in Ngata, Japan, occurred in one of the least active areas of the country.

“Second, the sequences of the large earthquake in Alaska in 1964 were scattered over an area comparable with half the area of New Zealand.”