A seismic hazard assessment and microzonation of Bundaberg

This thesis investigates the statistical seismic hazard that exists within the Bundaberg area and derives microzonation information for Bundaberg City, suitable for conjoint use with AS1170.4 - 1993, and its future replacements, in determining Earthquake Loading for design and construction engineering. A brief history of significant seismic events that have occurred in the Bundaberg area is provided, including presentation of an isoseismal map for the 1997 Bundaberg earthquake, and the regional geography is outlined. The effect of ground motion amplification and how it increases the seismic risk at sites within the Bundaberg City area is examined. The use of spectral ratios of ambient seismic noise, calculated from seismograms of microtremors, in characterising local site response to ground motion is discussed in detail. Specifically, horizontal to vertical spectral ratios (HVSR), otherwise referred to as Nakamura Spectra, are used to determine the local site responses of engineering interest (microzonation), for a 1 km grid of the Bundaberg City area. A methodology and associated computer software is developed to calculate Nakamura Spectra and to carry out the microzonation analysis. The results are presented in map form, suitable for viewing on a Geographical Information System (GIS). The Nakamura Spectra are also used to estimate the known depths of sedimentary deposits in the Bundaberg area. The estimated depths show a positive correlation with known depths thus verifying the applicability of the Nakamura Spectra for the purposes of microzonation.