Australian Seismic Site Conditions Map

The Australian Seismic Site Conditions Map (ASSCM) uses information about surficial geology (regolith) as a proxy for the potential behaviour of geological materials under the influence of seismic ground shaking, predominantly in the context of amplification of earthquake energy.The ASSCM represents a revision and upgrade of the existing National Regolith Site Classification Map of Australia (NRSCM) published in 2007 (McPherson & Hall, 2007). Key improvements to the new product include the integration of new and updated geological data in a more robust spatial reference frame. In addition, a fully documented workflow has been developed, enabling the product to be efficiently updated as required. Comparison of different scale input geological data sets demonstrates the power of higher resolution data to provide better discrimination of site conditions - an important factor in determining the reliability of hazard and risk modelling outputs. The implementation of a weathering intensity index captures the reduced strength (and possible minor increase in ground shaking potential) of substrate in bedrock-dominated environments. Accuracy and consistency checking of the ASSCM (and the NRSCM) against geotechnical data from the Newcastle (NSW) and Perth (WA) regions shows good agreement between the ASSCM site condition (site class) mapping and field measurements In both areas the ASSCM out-performs the existing NRSCM.The ASSCM represents a repeatable and publicly available data set representing Australian seismic site conditions. The generally improved resolution and spatial reliability relative to the existing NRSCM establish the ASSCM as a key input for incorporating seismic site conditions into seismic hazard analysis and modelling in Australia.