Quantification of seismic shaking variations due to source effects at soft soil sites in the Wellington region

Technical Abstract

Microearthquakes have recently been used in Wellington region to estimate relative site responses for the purpose of defining the ground shaking hazard. In these studies, the amplifications of ground motion at individual flexible sediment sites have varied by up to a factor of 5 depending on the earthquake. The purpose of this project has been to systematically examine the causes of the variation. Much of this variation in ground motion amplification has been found to be due to random scattering effects, and not simply related to earthquake location or mechanism.

The importance of random scattering means that while the average response of a site can be determined by measuring the response of a range of earthquakes, there will always be a degree of uncertainty in the actual response of a site in a particular earthquake