Authors / CoAuthors
Griffin, J. | Gerstenberger, M. | Allen, T. | Clark, D. | Cuthbertson, R. | Dimos, A. | Gibson, G. | Ghasemi, H. | Hoult, R. | Lam, N. | Leonard, M. | Mote, T. | Quigley, M. | Somerville, P. | Sinadinovski, C. | Stirling, M. | Venkatesan, S.
Abstract
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.
Product Type
document
eCat Id
123027
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
Canberra
ACT
2601
Australia
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Keywords
- ( Discipline )
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- earthquake hazard
- ( Discipline )
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- expert elicitation
- ( Product )
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- Published_External
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- HVC_144647
Publication Date
2018-10-10T03:16:01
Creation Date
2018-09-18T00:00:00
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final
Purpose
This Record is the second in the series of Records and datasets that support the release of the NSHA18 (overarching overview provided at ecat 123020)
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asNeeded
Topic Category
geoscientificInformation
Series Information
Record 2018/028
Lineage
Geoscience Australia develops the National Seismic Hazard Assessment (NSHA) for Australia. The NSHA defines the level of earthquake ground shaking across Australia that has a given likelihood of being exceeded in a given time period. Knowing how the ground-shaking hazard varies across Australia allows higher hazard areas to be identified and prioritised for the development of mitigation strategies so communities can be more resilient to earthquake events. The NSHA also provides key information to the Australian Government Building Codes Board, so buildings and infrastructure design standards can be updated to ensure they can withstand earthquake events in Australia. Geoscience Australia schedules the update to the NSHA with the update to the earthquake loading standard, so the committee can consider any changes to the seismic hazard risk of Australia, and whether the code needs to be amended to reflect this. The 2018 update was scheduled to inform the 2017 revision of the earthquake loading standard. Promotion of project via http://www.ga.gov.au/about/projects/safety/nsha
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[-44, -9, 112, 154]
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Service Information
Associations
Association Type - crossReference
The 2018 National Seismic Hazard Assessment: Model overview
eCat Identifier - 123020
Association Type - wasInformedBy
10% in 50 year seismic hazard map
eCat Identifier - 123132
Association Type - wasInformedBy
Selection and ranking of ground-motion models for the 2018 National Seismic Hazard Assessment of Australia: Summary of ground-motion data, methodology and outcomes
eCat Identifier - 123034
Association Type - wasInformedBy
The 2018 National Seismic Hazard Assessment for Australia – model input files
eCat Identifier - 123049
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