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Does PSHA Meet the Needs for Modern Engineering Design In Australia?

Created 17/10/2025

Updated 17/10/2025

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Damaging earthquakes in Australia and other regions characterised by low seismicity are considered low probability, high consequence events. Uncertainties in modeling earthquake occurrence rates and ground motions pose unique challenges to forecasting seismic hazard in these regions. In 2018 Geoscience Australia released its National Seismic Hazard Assessment (NSHA18). Results from the NSHA18 indicate significantly lower seismic hazard across almost all Australian localities at the 1/500 annual exceedance probability (AEP) relative to the factors in the Australian earthquake loading standard; the AS1170.4. Due to concerns that the 1/500 AEP hazard factors proposed in the NSHA18 would not assure life safety throughout the continent, the amended AS1170.4 (revised in 2018) retains seismic demands developed in the early 1990s and also introduces a minimum hazard design factor of Z = 0.08 g. The hazard estimates from the NSHA18 have challenged notions of seismic hazard in Australia in terms of the probability of damaging ground motions and raises questions as to whether current practices in probabilistic seismic hazard analysis (PSHA) deliver the outcomes required to protect communities in low-seismicity regions, such as Australia. By contrast, it is also important that the right questions are being asked of hazard modelers in terms of the provision of seismic demand objectives that are fit for purpose. In the United States and Canada, a 1/2475 AEP is used for national hazard maps due to concerns that communities in low-to-moderate seismicity regions are considerably more at risk to extreme ground-motions. The adoption of a 1/2475 AEP seismic demands within the AS1170.4 would bring it in to line with other international building codes in similar tectonic environments and would increase seismic demand factors to levels similar to the 1991 hazard map. This, together with other updates, may be considered for future revisions to the standard. Presented at the Technical Sessions of the 2021 Seismological Society of America Annual Meeting (SSA)

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Additional Info

Field Value
Title Does PSHA Meet the Needs for Modern Engineering Design In Australia?
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/1ae79a50-de41-4ee2-a0c1-2d721c0de1b7
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 08/04/2019
Geospatial Coverage
Map data © OpenStreetMap contributors
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      ],
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        -44.0
      ],
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      [
        112.0,
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      ],
      [
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      ]
    ]
  ],
  "type": "Polygon"
}
Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "Does PSHA Meet the Needs for Modern Engineering Design In Australia?". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/does-psha-meet-the-needs-for-modern-engineering-design-in-australia