The earthquake hazard in Dunedin: soils and foundations

Abstract

Dunedin is located in one of the least seismically active areas in New Zealand. However, while the frequency of severe earthquake shaking is considerably lower in Dunedin than for Christchurch or Wellington, strong shaking will occur in the city. Even the relatively small earthquake of 1974 caused about $2 million (1993 values) of damage, and larger, though infrequent earthquakes could cause many times this amount in direct damage and major disruption to the local economy.

This study attempts to quantify the seismic hazard of Dunedin by adopting current seismic hazard analysis techniques and applying them specifically to Dunedin.

Seismic hazard analysis involves three components: a Seismicity Model (a model of earthquake occurrence probability in regions close enough to affect the city), an Attenuation Model (energy loss and wave modification as the seismic waves travel to the basement rock under the city) and a Site Response Model (predicting the changes to the earthquake waves as they propagate up through the gravels, sands and silts underlying the city).