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An updated National Seismic Hazard Assessment for Australia: Are we designing for the right earthquakes?

Geoscience Australia (GA) has embarked on a project to update the seismic hazard model for Australia through the National Seismic Hazard Assessment (NSHA18) project. The draft NSHA18 update yields many important advances on its predecessors, including: 1) calculation in a full probabilistic framework using the Global Earthquake Model’s OpenQuake-engine; 2) consistent expression of earthquake magni-tudes in terms of moment magnitude, MW; 3) inclusion of epistemic uncertainty through the use of alterna-tive source models; 4) inclusion of a national fault-source model based on the Australian Neotectonic Features database; 5) the use of modern ground-motion models; and 6) inclusion of epistemic uncertainty on seismic source models, ground-motion models and fault occurrence and earthquake clustering models.


The draft NSHA18 seismic design ground motions are significantly lower than those in the current (1991-era) AS1170.4–2007 hazard map at the 1/500-year annual ground-motion exceedance probability (AEP) level. However, draft values at lower probabilities (i.e., 1/2475-year AEP) are entirely consistent, in terms of the percentage area of land mass exceeding different ground-motion thresholds, with other Stable Continental Regions (e.g., central & eastern United States). The large reduction in seismic hazard at the 1/500-year AEP level has led to engineering design professionals questioning whether the new draft design values will provide enough structural resilience to potential seismic loads from rare large earthquakes. This process underscores the challenges in developing national-scale probabilistic seismic hazard analyses (PSHAs) in slowly-deforming regions, where a 1/500-year AEP design level is likely to be much lower than the ANCOLD Maximum Credible Earthquake (MCE) ground motions. Consequently, a robust discussion among the Standards Australia code committee, hazard practitioners and end users is required to consider alternative hazard and/or risk objectives for future standards.


Site-specific PSHAs undertaken for owners and operators of extreme and high consequence dams generally require hazard evaluations at lower probabilities than for typical structural design as recommended in AS1170.4. However, modern national assessments, such as the NSHA18, can provide a benchmark in terms of recommended seismicity models, fault-source models, ground-motion models, as well as hazard values, for low-probability site-specific analyses. With a new understanding of earthquake processes in Australia leading to lower ground-motion hazard values for higher probability events (e.g., 1/500-year AEP), we should also ask whether the currently recommended design probabilities provide an acceptable level of seismic resilience to critical facilities (such as dams) and regular structures.


Abstract presented at the 2017 Australian National Committee on Large Dams (ANCOLD) Conference

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Identification info

Date (Creation)
2017-09-01T00:00:00
Date (Publication)
2024-03-19T22:33:31
Citation identifier
Geoscience Australia Persistent Identifier/https://pid.geoscience.gov.au/dataset/ga/113462

Cited responsible party
Role Organisation / Individual Name Details
Publisher

Commonwealth of Australia (Geoscience Australia)

Voice
Author

Allen, T.

Place and Communities Internal Contact
Author

Griffin, J.

Place and Communities Internal Contact
Author

Leonard, M.

External Contact
Author

Clark, D.

Place and Communities Internal Contact
Author

Ghasemi, H.

Place and Communities Internal Contact
Issue identification

Australian National Committee on Large Dams (ANCOLD) 2017 Conference, 26-27 October 2017 Hobart, TAS

Purpose

Conference Paper for 2017 Australian National Committee on Large Dams (ANCOLD) Conference

Status
Completed
Point of contact
Role Organisation / Individual Name Details
Point of contact

Commonwealth of Australia (Geoscience Australia)

Voice
Resource provider

Place and Communities Division

External Contact
Point of contact

Allen, T.

Place and Communities Internal Contact
Spatial representation type
Grid
Topic category
  • Geoscientific information

Extent

Extent

N
S
E
W


Maintenance and update frequency
As needed

Resource format

Title

Product data repository: Various Formats

Website

Data Store directory containing the digital product files

Data Store directory containing one or more files, possibly in a variety of formats, accessible to Geoscience Australia staff only for internal purposes

theme.ANZRC Fields of Research.rdf
  • EARTH SCIENCES

Keywords
  • probabilistic seismic hazard analysis - PSHA

Keywords
  • design codes

Keywords
  • neotectonic faults

Keywords
  • Published_External

Resource constraints

Title

Creative Commons Attribution 4.0 International Licence

Alternate title

CC-BY

Edition

4.0

Website

http://creativecommons.org/licenses/

Access constraints
License
Use constraints
License
Other constraints

© Commonwealth of Australia (Geoscience Australia) 2017

Resource constraints

Classification
Unclassified
Language
English
Character encoding
UTF8

Distribution Information

Distributor contact
Role Organisation / Individual Name Details
Distributor

Commonwealth of Australia (Geoscience Australia)

Voice facsimile
OnLine resource

Link to Conference Proceedings (page 248)

Link to Conference Proceedings (page 248)

Distribution format
OnLine resource

Link to Abstract

Link to Abstract

Distribution format

Resource lineage

Statement

Conference Paper for 2017 Australian National Committee on Large Dams (ANCOLD) Conference

Hierarchy level
Model

Metadata constraints

Classification
Unclassified

Metadata

Metadata identifier
urn:uuid/80b86f4c-368b-4370-8fdd-72abcde3400d

Title

GeoNetwork UUID

Contact
Role Organisation / Individual Name Details
Point of contact

Commonwealth of Australia (Geoscience Australia)

Voice
Owner

Allen, T.

Place and Communities Internal Contact
Point of contact

Allen, T.

Place and Communities Internal Contact

Type of resource

Resource scope
Document
Name

Conference Abstract

Alternative metadata reference

Title

Geoscience Australia - short identifier for metadata record with

uuid

Citation identifier
eCatId/113462

Metadata linkage

https://internal.ecat.ga.gov.au/geonetwork/srv/eng/search?uuid=80b86f4c-368b-4370-8fdd-72abcde3400d

Point-of-truth metadata URL

Metadata linkage

https://ecat.ga.gov.au:80/geonetwork/srv/eng/catalog.search#/metadata/80b86f4c-368b-4370-8fdd-72abcde3400d

Metadata linkage

https://ecat.ga.gov.au/geonetwork/dashboard/eng/catalog.search#/metadata/80b86f4c-368b-4370-8fdd-72abcde3400d

Metadata linkage

https://ecat.ga.gov.au/geonetwork/srv/eng/catalog.search#/metadata/80b86f4c-368b-4370-8fdd-72abcde3400d

Date info (Creation)
2017-09-01T07:27:20
Date info (Revision)
2018-03-01T04:10:38

Metadata standard

Title

AU/NZS ISO 19115-1:2014

Metadata standard

Title

ISO 19115-1:2014

Metadata standard

Title

ISO 19115-3

Edition date
2015-07-01T00:00:00
Title

Geoscience Australia Community Metadata Profile of ISO 19115-1:2014

Edition

Version 2.0, April 2015

 
 

Spatial extent

N
S
E
W


Keywords

design codes neotectonic faults
theme.ANZRC Fields of Research.rdf
EARTH SCIENCES

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