Seismic Site Classification and Earthquake Hazard in the Sydney Region - Milestone Report 1  

Authors / CoAuthors

McPherson, A.A. | Burbidge, D.R.

Abstract

Geoscience Australia (GA) was engaged by Sydney Water Corporation (SW) to review existing geological, geophysical and geotechnical data from the Sydney region in an effort to better understand seismic hazard in SW's area of operations. The goal is to improve SW's understanding of the level of earthquake risk to their infrastructure in order to support their asset management practices. Of particular interest is improving SW's understanding of asset damage or loss and potential network disruption, following a large earthquake. The project outputs comprise two milestone reports. This document represents the first of these, and presents an earthquake hazard assessment of the SW area of operations based on the bedrock hazard definition outlined in the Australian Standard AS1170.4-2007. It also includes a seismic site classification of the soil conditions across the area based on mapped geology. The second milestone report, to be delivered by the end of June 2010, will incorporate a full probabilistic seismic hazard assessment of the SW area of operations, in addition to the hazard maps presented in the current report. The opening chapter of this first milestone report provides brief background information on earthquakes and the geology in the Sydney region. The second chapter covers the development and validation of the seismic site classification maps for the Sydney region. Two maps were produced; one created using the United States National Earthquake Hazard Reduction Program (NEHRP) classification scheme and one using the Australian Earthquake Loading Standard (AS1170.4-2007) classification scheme. Assessment of both the modified NEHRP and AS1170.4-2007 Australian Standard classifications have shown that both can be considered to satisfactorily represent the distribution of materials with varying potential to amplify earthquake ground shaking. This has been established by reclassifying existing mapped geology according to each classification, and testing the predicted classifications against independently acquired data from sub-surface investigations in the region. The final chapter presents maps showing the expected level of earthquake hazard in the SW area of operations using the site classification schema, hazard factors and tables given in AS1170.4-2007. A total of six hazard maps for SW's area of operations are presented for three spectral periods (0 s, 0.2 s and 1.0 s) and return periods of 500 years and 800 years. The results show that ground shaking at 0.2 s spectral period generally represents the highest hazard at 500 year and 800 year return periods. For areas with similar AS1170.4-2007 bedrock hazard values the environments characterised by Cenozoic sedimentary units have the highest earthquake hazard. While every effort has been made to ensure that the maps provided are as reliable as possible, GA cannot guarantee the accuracy or completeness of the information presented as the products are subject to the limitations of the available input data and changes in best practice methods. Therefore, this information should not be solely relied upon when making commercial decisions. In particular, local site conditions can be highly variable at the scale of individual structures, and only a site specific assessment can truly characterise the site conditions and thus the hazard at any given site.

Product Type

document

eCat Id

70233

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Keywords

• GA PublicationProfessional Opinion

( Theme )

• earthquakes

( Theme )

• geohazards

• AU-NSW

Australian and New Zealand Standard Research Classification (ANZSRC)

• Earth Sciences

• Published_Internal

Publication Date

2010-01-01T00:00:00

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Australian Government Security ClassificationSystem    

Classification - unclassified

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Special, MOU, etc.

Access - restricted

Use - license

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unknown

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geoscientificInformation

Series Information

Professional Opinion 2010/002

Lineage

Unknown

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Extents

[-36.0, -32.0, 150.0, 156.0]

Reference System

Spatial Resolution

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