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.

The 2018 National Seismic Hazard Assessment (NSHA18) is a flagship Geoscience Australia product, used to support the decisions of the Australian Building Codes Board and Standards Australia to ensure buildings and infrastructure are built to withstand seismic events in Australia. It is also important for the insurance sector and provides a baseline for setting national reinsurance premiumsguides the level of reinsurance premiums. The National Seismic Hazard Assessment Earthquake Epicentre Catalogue (NSHA18-Cat) of historical earthquakes is the authoritative catalogue underpinning the NSHA18. The NSHA18-Cat is compiled from Australian and international sources and combines the highest quality epicentres and magnitudes for the assessment of earthquake hazard in Australia. For the first time in an Australian national seismic hazard assessment, earthquake magnitudes are uniformly expressed in the moment magnitude MW scale, using Australian-specific magnitude conversion equations appropriate for several common magnitude types. The magnitude harmonisation represents a significant advance in our ability to represent earthquake hazard in a uniform manner throughout the country. Key points and advances on the NSHA18-Cat include: - The addition of almost three decades worth of additional earthquake data gathered by seismic networks across the Australian continent, relative to hazard assessments from the early 1990s. - The use of the International Seismological Centre-Global Earthquake Model Catalogue (Version 5) for regional plate boundary source zones; - An improved methodology for revising local magnitudes due to the historical use of inappropriate magnitude attenuation formulae using a consistent and objective methodology; - The development of conversion equations from original magnitude types to MW specific for the Australian earthquake catalogue. This ensures consistency between rates of earthquake recurrence and ground-motion models in hazard calculations; - The development of new magnitude completeness models in terms of MW. The combination of these new data and advances demonstrates global best practice and evidence based science for undertaking national-scale earthquake hazard assessments. The earthquake epicentre solutions are provided in simple comma separated value and shapefile formats and are attached to this report.

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

<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 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).

Located within an intraplate setting, continental Australia has a relatively low rate of seismicity compared with its surrounding plate boundary regions. However, the plate boundaries to the north and east of Australia host significant earthquakes that can impact Australia. Large plate boundary earthquakes have historically generated damaging ground shaking in northern Australia, including Darwin. Large submarine earthquakes have historically generated tsunami impacting the coastline of Australia. Previous studies of tsunami hazard in Australia have focussed on the threat from major subduction zones such as the Sunda and Kermadec Arcs. Although still subject to uncertainty, our understanding of the location, geometry and convergence rates of these subduction zones is established by global tectonic models. Conversely, actively deforming regions in central and eastern Indonesia, the Papua New Guinea region and the Macquarie Ridge region are less well defined, with deformation being more continuous and less easily partitioned onto discrete known structures. A number of recently published geological, geodetic and seismological studies are providing new insights into present-day active tectonics of these regions, providing a basis for updating earthquake source models for earthquake and tsunami hazard assessment. This report details updates to earthquake source models in active tectonic regions along the Australian plate boundary, with a primary focus on regions to the north of Australia, and a subsidiary focus on the Puyesgur-Macquarie Ridge-Hjort plate boundary south of New Zealand. The motivation for updating these source models is threefold: 1. To update regional source models for the 2018 revision of the Australian probabilistic tsunami hazard assessment (PTHA18); 2. To update regional source models for the 2018 revision of the Australian national seismic hazard assessment (NSHA18); and 3. To provide an updated database of earthquake source models for tsunami hazard assessment in central and eastern Indonesia, in support of work funded through the Department of Foreign Affairs and Trade (DFAT) DMInnovation program.

This Geoscience Australia Record contains technical data and input files that, when used with the Global Earthquake Model’s (GEM’s) OpenQuake-engine probabilistic seismic hazard analysis software (Pagani et al., 2014), will enable end users to explore and reproduce the 2018 National Seismic Hazard Assessment (NSHA18) of Australia (Allen et al., 2018a). This report describes the NSHA18 input data only and does not discuss the scientific rationale behind the model development. These details are provided in Allen et al. (2018a) and references therein.

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.

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

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).