The Dunedin earthquake, 9 April, 1974

Abstract

The earthquake of 9 April, 1974 was the strongest experienced in the Dunedin area in historic times. It was centred at sea about 10 km south of the city and had a magnitude of 5.0. The felt intensity reached MMVII in the St. Clair area, where a ground acceleration of 0.27 g was recorded. Variations in felt intensity were determined from a survey of grocery stores. The intensity decreased rapidly away from a maximum on the alluvial ground of the southern suburbs and correlated strongly with the underlying rock type. The number of claims received by the Earthquake and War Damage Commission was extraordinarily large for an earthquake of this magnitude. Damage, generally of a rather minor nature, was reported from all parts of the city, but was greatly concentrated in the South Dunedin - St. Clair area. About half of the 3000 claims received included chimney damage. The effects of the earthquake highlight the need to assess the safety of public buildings in Dunedin, particularly those sited on areas of thick alluvium.