<div>One of the key challenges in assessing earthquake hazard in Australia is understanding the attenuation of ground-motion through the stable continental crust. There are now a small number of ground-motion models (GMMs) that have been developed specifically to estimate ground-motions from Australian earthquakes. These GMMs, in addition to models developed outside Australia, are considered here for use in the updated national seismic hazard assessment of Australia. An updated and extended suite of ground-motion data from small-to-moderate Australian earthquakes are used to assess the suitability of the candidate models for use in the Australian context. Recorded spectral intensities are compared with those predicted by the GMMs. Both qualitative and quantitative approaches are considered for such comparisons. The goodness-of-fit results vary significantly among different GMMs, spectral periods and distance ranges; however, overall, the Australian-specific GMMs seem to perform reasonably well in estimating the level of ground shaking for earthquakes in Australia. This paper was presented to the 2022 Australian Earthquake Engineering Society (AEES) Conference 24-25 November (https://aees.org.au/aees-conference-2022/)

<div>Geoscience Australia, together with contributors from the wider Australian seismology community, have produced a new National Seismic Hazard Assessment (NSHA23), recommended for inclusion in proposed updates to Standards Australia’s&nbsp;AS1170.4. NSHA23 builds on the model framework developed for NSHA18, and incorporates scientific advances and stakeholder feedback received since development of that model. Key changes include: further refinement and homogenisation of the earthquake catalogue; revisions to the fault source model through inclusion of newly identified faults and revised activity rates on some faults; assessment of ground motion models through quantitative comparison against observations; and inclusion of a specific ground motion model for shaking from plate-boundary earthquakes in northern Australia. Expert elicitation was used to capture epistemic uncertainty surrounding model choices. The elicitation focused on decision points that sensitivity analysis had shown were more important for hazard, where new models had been developed, and where model choices had been controversial in NSHA18. Key questions included which catalogue to use as the basis for calculating hazard, the weighting of different source model classes (background, regional, seismotectonic, smoothed seismicity and smoothed seismicity with faults), and the selection and weighting of ground motion models for different tectonic regions. NSHA23 hazard results for capital cities show minor changes compared with NSHA18, with the exception of Darwin. Here the ground motion with a 10% probability of exceedance in 50 years increases significantly, a result that is attributed to inclusion of a new, more realistic ground motion model for plate-boundary earthquakes in this unique tectonic setting.</div><div><br>This paper was presented to the 2023 Australian Earthquake Engineering Conference 23-25 November 2023 (https://aees.org.au/aees-conference-2023/)</div>

<div>Dam owners and operators must consider a range of hazards for the design and maintenance of infrastructure assets – including seismic hazards. In 2018, Geoscience Australia completed its National Seismic Hazard Assessment (the NSHA). This assessment used best-practice probabilistic approaches and resulted in considerably lower hazard estimates than previously considered applicable for Australia. This assessment, and subsequent site-specific assessments conducted on behalf of the dam industry have yielded divergent estimates in hazard. This has caused confusion and concern amongst the dam engineering community. Herein, we unpack the rationale for these large discrepancies, and identify best practices for the treatment of earthquake catalogues when undertaking probabilistic seismic hazard assessments for extreme-consequence facilities. A short summary of the 2023 update to the NSHA is also provided. Presented at the 2023 Australian National Committee on Large Dams (ANCOLD) Conference

An earthquake catalogue based on the moment magnitude scale is required for calculation of seismic hazard in Australia. However, the estimation of moment magnitudes for small to moderate sized earthquakes is not a routine process at seismic observatories, resulting in a catalogue mainly based on the local magnitude scale for Australia. In this study we explore the application of an automated procedure to estimate moment magnitudes by minimizing the misfit between observed and synthetic displacement spectra. We compile a reference catalogue of 15 earthquakes with moment magnitude values between 3.8 and 5.4 which were based on previous studies. The moment magnitudes were then recalculated and we find that the estimated moment magnitudes are in good agreement with reference values with differences mainly lower than 0.2. However, the reported local magnitudes of the selected events are consistently higher than the reference values with differences between 0.3 and 1.0. The automated procedure will be applied to compute moment magnitudes of the well recorded events in Australia, and to derive a scaling relation between local magnitude and moment magnitude. This abstract was submitted and presented to the 2016 Australian Earthquake Engineering Society Conference (AEES) ( https://aees.org.au/aees-asian-seismological-commission-conferences/)