Effects Of Earthquakes In Alaska And Japan

Press, Volume CIII, Issue 30602, 19 November 1964, Page 15

Effects Of Earthquakes In Alaska And Japan

Damage to buildings in Anchorage (Alaska) and Niigata (Japan) during earthquakes earlier this year were described at the civil defence controllers’ course by Mr B. W. Spooner, assistant chief civil engineer to the Ministry of Works.

Mr Spooner showed photographs which he took during a visit to Anchorage a month after the earthquake there, and photographs taken at Niigata just after its earthquake by Dr. B. Falconer, a New Zealand engineer working on a U.N.E.S.C.O. fellowship at the Building Research Institute of Japan, Tokyo. The Anchorage earthquake

was the largest ever recorded on the North American continent; the Niigata earthquake was smaller, but still about as big as the Hawke’s Bay earthquake, said Mr Spooner.

In Anchorage, many build-

ings had been severely damaged structurally—by the earthquake itself or through slumping of the edge of the terrace on which much of the city was built. While the reinforced-con-crete buildings mostly stood up to the earthquake very well, a building put up on the central lift-pillar principle, with the floors jacked up from the ground, had collapsed completely. The allurel material of the terrace had filtered out the high-frequency components of the shock waves, Mr Spooner said. This, he explained, meant that tall buildings were likely to be relatively more affected than shorter ones. He illustrated the point with models. Weatherboard houses were mostly relatively undamaged, even when the ground had slumped from underneath them, he said.

Masonry Buildings Many masonry buildings had crumbled, providing further evidence for the general belief among engineers that this type of building was bad unless very carefully designed and supervised. Many of the tallest buildings had stood up to the shock as far as their vertical members were concerned, but horizontal members were badly affected.

In a high-class residential suburb built on the edge of the terrace or on its slope, many buildings had been left at odd angles through slumping.

Several medium-sized buildings had cracks in vertical members while most of the rest of the structure was intact. This indicated that more allowance could have been made for the effects of a possible earthquake, and was a lesson for New Zealand.

In Niigata, there had been few if any structural failures, but whole buildings had been toppled. The effect of the earthquake had been a classic example of the need for proper foundations when building on unsuitable ground, for practically all the damage had occurred on a low-lying sandy area where the water table was very close to the surface.