<div>An earthquake catalogue based on the moment magnitude scale (<em>M</em>W) is a prerequisite for global best practice seismic hazard analyses. The 2018 National Seismic Hazard Assessment (NSHA18) was the first national-scale seismic hazard assessment for Australia to apply magnitude conversions to express earthquake magnitudes uniformly in terms of <em>M</em>W. This approach led to the single-biggest change in seismic hazard estimates between Geoscience Australia-led national seismic-hazard models. Between the 2012 and 2018 assessments, the hazard reduced because of: 1) the general reduction in the number of earthquakes of magnitude 4.0 and larger due to the correction of local magnitudes (<em>M</em>L) and subsequent conversion to <em>M</em>W, and; 2) the increase in the Gutenberg-Richter <em>b</em>-value due to the non-linear conversion of local magnitudes <em>M</em>L to <em>M</em>W.</div><div>Using a new continental-scale attenuation model, independent assessment of <em>M</em>W has been performed for over 300 earthquakes recorded between 1990 and September 2024. After recalculating <em>M</em>L for the same earthquakes using improved filtering and time-domain windowing criteria, the <em>M</em>W catalogue is used to test and validate the <em>M</em>L to <em>M</em>W conversion equations used in the 2023 National Seismic Hazard Assessment (NSHA23). The earthquakes are partitioned into their regional magnitude polygons as applied by Geoscience Australia in its real-time operations; notionally central and western Australia, South Australia (Mt Lofty and Flinders Ranges) and eastern Australia. The performance NSHA23 <em>M</em>L to <em>M</em>W conversion equation is then assessed for each of these magnitude regions. Overall, the NSHA23 <em>M</em>L to <em>M</em>W conversion performs very well relative to continental-scale earthquake dataset. The sensitivity of this conversion to an earthquake’s static stress drop is also assessed. There is evidence that minor adjustments could be applied to the NSHA23 <em>M</em>L–<em>M</em>W conversion equation for larger-magnitude events with high stress drops.</div><div><br></div> Presented at the Australian Earthquake Engineering Society (AEES) National Conference 2024

<div>This Geoscience Australia Record contains technical data and input files that, when used with the Global Earthquake Model’s (GEM’s) <em>OpenQuake-engine</em> probabilistic seismic hazard analysis software (Pagani<em> et al.</em>, 2023), will enable end users to explore and reproduce the 2023 National Seismic Hazard Assessment (NSHA23) of Australia (Allen<em> et al.</em>, 2023b). Output data, as calculated by Geoscience Australia using Version 3.16.1 of the <em>OpenQuake-engine</em>, are also provided. This report describes the NSHA23 input and output data only and does not discuss the scientific rationale behind the model development or the development of the NSHA23 earthquake catalogue. These details are provided in Allen<em> et al.</em> (2023b) and (Allen<em> et al.</em>, 2024), and respective references therein. The NSHA23 provides estimates of seismic hazard for the six Australian states and two mainland territories. However, it does not provide updated hazard factors for Australia’s Antarctic and other offshore territories (e.g., Christmas Island, Cocos Island, Heard Island, Lord Howe Island, Macquarie Island and Norfolk Island).</div>