Abstract:
This thesis presents the dynamic site characterisation of various sites across the Hauraki Plains using Horizontal to Vertical Spectral Ratio (HVSR) ambient vibration method. Deep soils (alluvium and gravels) overlying stiffer, consolidated sediments or rocks may lead to amplification of ground shaking and seismic site effects. Such deposits are rife throughout the Hauraki Plains and coupled with the active Kerepehi Fault, situated centrally in Hauraki Plains, there is indeed a concern for seismic hazard within the Hauraki Plains and adjacent cities such as Hamilton, Auckland and Tauranga. There is a lack of prior knowledge regarding dynamic properties of the deposits in the Hauraki Plains. Existing geological, geotechnical and seismic site characterisation data of various basins in New Zealand were collected to establish an overall level of current knowledge, find potential gaps in knowledge and highlight areas where research is a priority. The Hauraki Plains was identified as a key area of interest due to its proximity to major city centres and the lack of site characterisation knowledge. The HVSR method was used across the Hauraki Plains to determine variations in fundamental period, better constrain the basin structure and provide site classification metrics based on New Zealand Earthquake Loading standards (NZS1170.5:2004). The HVSR method was able to estimate the fundamental site periods at each location and a good correlation between inferred depths of the Hauraki Rift from existing geophysical models and fundamental site periods was established. The information collected in this study will be used to inform site classification across the Hauraki region for inputs into seismic design, seismic hazard analysis and modelling. These can be used for civil defence response planning and the study additionally highlights areas where further study and research should be directed.