2001 – Site Specific Probabilistic Seismic Hazard Assessment of Six Victoria Dams

R.A. Vreugdenhil, G. Gibson, M.R. Jorgensen, A. Brown and P.G. Somerville

For the first time for any region of Australia, a modern site specific seismic hazard assessment has been completed for six major dams, incorporating fault mapping and trenching to assess fault source characterisation and likely slip rates. A combination of modern ground motion attenuation relations appropriate for stable continental regions was used. The work was performed in a probabilistic context, and includes significant advances in Australia for all aspects of seismic hazard evaluation. The study found that for a short recurrence interval, a large earthquake distant from the site may have a greater probability of contributing to a low PGA, than a low magnitude event closer to the site. At longer recurrence intervals, the magnitudes that contribute most to the hazard have dropped significantly below the previous levels of magnitude for several storages. The outcome of this work is an understanding of the likely strength and duration of ground shaking at each of the six dam sites for any design earthquake, and an understanding of the contribution of each source zone to the seismic hazard. Ground motion parameters produced by the study have been used as a reasonable basis for subsequent seismic analysis of embankments, towers and spillway structures.