<div>This document provides a summary of fault parameterisation decisions made for the faults comprising the fault-source model (FSM) for 2023 National Seismic Hazard Assessment (NSHA23).&nbsp;As with the NSHA18, the FSM for the NSHA23 implementation requires the following parameters: simplified surface trace, dip, dip direction, and slip-rate. As paleoseismic data exist for only a few of the approximately 400 faults within the Australian Neotectonic Features database, we use the Neotectonic Domains model as a framework to parametrise uncharacterised faults.</div>

This ecat record refers to the data described in ecat record 123048. The data, supplied in shapefile format, is an input to the 2018 National Seismic Hazard Assessment for Australia (NSHA18) product (ecat 123020) and the 2018 Probabilistic Tsunami Hazard Assessment for Australia (PTHA18) product (ecat 122789).

The 2018 National Seismic Hazard Assessment (NSHA18) aims to provide the most up-to-date and comprehensive understanding of seismic hazard in Australia. As such, NSHA18 includes a range of alternative models for characterising seismic sources and ground motions proposed by members of the Australia earthquake hazard community. The final hazard assessment is a weighted combination of alternative models. This report describes the use of a structured expert elicitation methodology (the ‘Classical Model’) to weight the alternative models and presents the complete results of this process. Seismic hazard assessments are inherently uncertain due to the long return periods of damaging earthquakes relative to the time period of human observation. This is especially the case for low-seismicity regions such as Australia. Despite this uncertainty, there is a demand for estimates of seismic hazard to underpin a range of decision making aimed at reducing the impacts of earthquakes to society. In the face of uncertainty, experts will propose alternative models for the distribution of earthquake occurrence in space, time and magnitude (i.e. seismic source characterisation), and how ground shaking is propagated through the crust (i.e. ground motion characterisation). In most cases, there is insufficient data to independently and quantitatively determine a ‘best’ model. Therefore it is unreasonable to expect, or force, experts to agree on a single consensus model. Instead, seismic hazard assessments should capture the variability in expert opinion, while allowing that not all experts are equally adept. Logic trees, with branches representing mutually exclusive models weighted by expert opinion, can be used to model this uncertainty in seismic hazard assessment. The resulting hazard assessment thereby captures the range of plausible uncertainty given current knowledge of earthquake occurrence in Australia. For the NSHA18, experts were invited to contribute peer-reviewed seismic source models for consideration, resulting in 16 seismic source models being proposed. Each of these models requires values to be assigned to uncertain parameters such as the maximum magnitude earthquake expected. Similarly, up to 20 published ground motion models were identified as being appropriate for characterising ground motions for different tectonic regions in Australia. To weight these models, 17 experts in seismic hazard assessment, representative of the collective expertise of the Australian earthquake hazard community, were invited to two workshops held at Geoscience Australia in March 2017. At these workshops, the experts each assigned weights to alternative models representing their degree of belief that a particular model is the ‘true’ model. The experts were calibrated through a series of questions that tested their knowledge of the subject and ability to assess the limits to their knowledge. These workshops resulted in calibrated weights used to parameterise the final seismic source model and ground motion model logic trees for NSHA18. Through use of a structured expert elicitation methodology these weights have been determined in a transparent and reproducible manner drawing on the full depth of expertise and experience within the Australia earthquake hazard community. Such methodologies have application to a range of uncertain problems beyond the case of seismic hazard assessment presented here.

Geoscience Australia, together with contributors from the wider Australian seismology community, has produced a National Seismic Hazard Assessment (NSHA18) that is intended as an update to the 2012 National Seismic Hazard Maps (NSHM12; Burbidge, 2012; Leonard et al., 2013). This Geoscience Australia Record provides an overview of the development of the NSHA18. Time-independent, mean seismic design values are calculated on Standards Australia’s AS1170.4 Soil Class Be (at VS30=760 m/s) for the horizontal peak ground acceleration (PGA) and for the geometric mean of the spectral accelerations, Sa(T), for T = 0.1, 0.2, 0.3, 0.5, 1.0, 2.0 and 4.0 s over a 15-km national grid spacing. Hazard curves and uniform hazard spectra are also calculated for key localities. Maps of PGA, in addition to Sa(0.2 s) and Sa(1.0 s) and for a 10% probability of exceedance in 50 years (Figure A). Additional maps and seismic hazard products are provided in a separate Geoscience Australia Record (Allen, 2018). The NSHA18 update yields many important advances over its predecessors, including: - the calculation in a full probabilistic framework (Cornell, 1968) using the Global Earthquake Model Foundation’s OpenQuake-engine (Pagani et al., 2014); - the consistent expression of earthquake magnitudes in terms of moment magnitude, MW; - inclusion of a national fault-source model based on the Australian Neotectonic Features database (Clark et al., 2016); - the inclusion of epistemic (i.e. modelling) uncertainty: - through the use of multiple alternative source models; - on magnitude-recurrence distributions; - fault recurrence and clustering models; - on maximum earthquake magnitudes for both fault and area sources through an expert elicitation workshop; and - the use of modern ground-motion models, capturing the epistemic uncertainty on ground motion through an expert elicitation workshop.

Data used to generate the National Seismic Hazard Assessments (NSHA). Data includes: original and modified earthquake catalogues, earthquake rate models, probabilistic seismic hazard outputs. The most recent assessment was completed in 2018 and can be viewed on Geoscience Australia's <a href="http://www.ga.gov.au/about/projects/safety/nsha">National Seismic Hazard Assessment (NSHA) Internet Page</a> <b>Value: </b> Data used to generate the NSHA <b>Scope: </b>Continental scale

Geoscience Australia, together with contributors from the wider Australian seismology community, has produced a National Seismic Hazard Assessment (NSHA18) that is intended as an update to the 2012 National Seismic Hazard Maps (NSHM12; Burbidge, 2012; Leonard et al., 2013). This Geoscience Australia Record provides an overview of the development of the NSHA18. Time-independent, mean seismic design values are calculated on Standards Australia’s AS1170.4 Soil Class Be (at VS30=760 m/s) for the horizontal peak ground acceleration (PGA) and for the geometric mean of the spectral accelerations, Sa(T), for T = 0.1, 0.2, 0.3, 0.5, 1.0, 2.0 and 4.0 s over a 15-km national grid spacing. Hazard curves and uniform hazard spectra are also calculated for key localities. Maps of PGA, in addition to Sa(0.2 s) and Sa(1.0 s) and for a 10% probability of exceedance in 50 years (Figure A). Additional maps and seismic hazard products are provided in a separate Geoscience Australia Record (Allen, 2018). The NSHA18 update yields many important advances over its predecessors, including: - the calculation in a full probabilistic framework (Cornell, 1968) using the Global Earthquake Model Foundation’s OpenQuake-engine (Pagani et al., 2014); - the consistent expression of earthquake magnitudes in terms of moment magnitude, MW; - inclusion of a national fault-source model based on the Australian Neotectonic Features database (Clark et al., 2016); - the inclusion of epistemic (i.e. modelling) uncertainty: - through the use of multiple alternative source models; - on magnitude-recurrence distributions; - fault recurrence and clustering models; - on maximum earthquake magnitudes for both fault and area sources through an expert elicitation workshop; and - the use of modern ground-motion models, capturing the epistemic uncertainty on ground motion through an expert elicitation workshop.

The 10% in 50 year seismic hazard map is the key output from the 2018 National Seismic Hazard Assessment for Australia (NSHA18) as required for consideration by the Standards Australia earthquake loading committee AS1170.4

This data is the output from the model assessment for the 2018 National Seismic Hazard Assessment for Australia (NSHA18) product (refer eCat 123020 for overview of product). This data is provided in multiple formats and is supported by accompanying maps to illustrate the seismic hazard (refer description of the model output at eCat 123028). The data is the output from the modelling process described in eCat 123049 which is in turn informed by GA Records relating to the expert elicitation workshop (eCat 123027), ground motion model selection (ecat 123034), earthquake epicentre catalogue (eCat 123041) and earthquake sources (eCat 123048).

This dataset is a key input to the development of the Australian National Seismic Hazard Assessment for 2018 (NSHA18).

Geoscience Australia, together with contributors from the wider Australian seismology community, has produced a National Seismic Hazard Assessment (NSHA18) that is intended as an update to Geoscience Australia’s 2012 National Seismic Hazard Maps (NSHM12; Burbidge, 2012) and its 2013 update (Leonard et al., 2013). The update at this time is intended to take advantage of recent developments in earthquake hazard research and to ensure the hazard model uses evidence-based science. This Geoscience Australia Record provides an overview of the output datasets generated through the development of the NSHA18. Time-independent, mean seismic design values are calculated on Standards Australia’s AS1170.4 Soil Class Be for the horizontal peak ground acceleration (PGA) and for the geometric mean of the spectral accelerations, Sa(T), for T = 0.1, 0.2, 0.3, 0.5, 1.0, 2.0 and 4.0 s over a 15-km national grid spacing. Hazard curves and uniform hazard spectra are also calculated for key localities at the10% and 2% probability of exceedance in 50-year hazard levels. Uniform-probability seismic hazard maps of PGA, in addition to all spectral periods, are provided for 10% and 2% probability of exceedance in 50 years. A Python script is provided to enable end users to interpolate hazard curve grids and to export site-specific hazard information given an input location and probability of exceedance (in the case of uniform hazard spectra). Additionally, geographic information system (GIS) datasets are provided to enable end users to view and interrogate the NSHA18 outputs on a spatially enabled platform. This is the most complete data publication for any previous Australian National Seismic Hazard Assessment. It is intended to ensure the NSHA18 outputs are openly available, discoverable and accessible to enable end-users to integrate these data into their own applications.