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This paper describes the methods used to define earthquake source zones and calculate their recurrence parameters (a, b, Mmax). These values, along with the ground motion relations, effectively define the final hazard map. Definition of source zones is a highly subjective process, relying on seismology and geology to provide some quantitative guidance. Similarly the determination of Mmax is often subjective. Whilst the calculation of a and b is quantitative, the assumptions inherent in the available methods need to be considered when choosing the most appropriate one. For the new map we have maximised quantitative input into the definition of zones and their parameters. The temporal and spatial Poisson statistical properties of Australia's seismicity, along with models of intra-plate seismicity based on results from neotectonic, geodetic and computer modelling studies of stable continental crust, suggest a multi-layer source zonation model is required to account for the seismicity. Accordingly we propose a three layer model consisting of three large background seismicity zones covering 100% of the continent, 25 regional scale source zones covering ~50% of the continent, and 44 hotspot zones covering 2% of the continent. A new algorithm was developed to calculate a and b. This algorithm was designed to minimise the problems with both the maximum likelihood method (which is sensitive to the effects of varying magnitude completeness at small magnitudes) and the least squares regression method (which is sensitive to the presence of outlier large magnitude earthquakes). This enabled fully automated calculation of a and b parameters for all sources zones. The assignment of Mmax for the zones was based on the results of a statistical analysis of neotectonic fault scarps.

This document presents an assessment of two earthquake scenarios in Melbourne. The two earthquake scenarios are considered the maximum magnitude earthquakes possible on the two fault structures; the Beaumaris Monocline and the Selwyn Fault. The assessments are based on using GA's earthquake risk modelling software, EQRM. The software is an open-source code that is capable of modelling earthquake scenario ground motion and scenario loss. Necessary inputs include the geometry of the fault structures, appropriate ground-motion and site classification models for the area concerned and exposure information describing the built environment. Impact assessment outputs include ground shaking intensity and residential loss estimates. The information from this scenario assessment can be used to inform emergency management planning and preparation in Victoria and support the national understanding of earthquake impact.

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Legacy product - no abstract available