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  • G E O S C I E N C E A U S T R A L I A

    Edited by Dan Clark

    APPLYING GEOSCIENCE TO AUSTR ALIA’S MOST IMPORTANT CHALLENGES

    Record

    2009/11

    Potential geologic sources of seismic hazard in the Sydney Basin

    GeoCat # 65991

    Proceedings volume of a one day workshop

  • Potential geologic sources of seismic hazard in the Sydney Basin

    geology

    geomorphology

    seismicity

    hazard studies

    future directions

    Proceedings volume of a one day workshop:

    Wednesday 13th April 2005

    GEOSCIENCE AUSTRALIA RECORD 2009/11

    Workshop coordinator: Dan Clark1

    1. Natural Hazard Impacts Project, Geospatial and Earth Monitoring Division, Geoscience Australia. Email: dan.clark@ga.gov.au.

  • Seismic Hazard in Sydney Proceedings of the one day workshop

    ii

    Department of Resources, Energy and Tourism Minister for Resources and Energy: The Hon. Martin Ferguson, AM MP Secretary: Mr John Pierce Geoscience Australia Chief Executive Officer: Dr Neil Williams PSM © Commonwealth of Australia, Geoscience Australia, 2009 This material is copyright Commonwealth of Australia. Other than the Coat of Arms and departmental logo, you may reproduce, distribute, adapt and otherwise freely deal with this material for all purposes without charge on the condition that you include the acknowledgement "© Commonwealth of Australia 2008, Potential geologic sources of seismic hazard in the Sydney Basin" on all uses. You may not sub-licence this material or use it in a misleading context. While every effort has been made to ensure accuracy, the Commonwealth does not accept any responsibility for the accuracy, completeness or currency of this material, and will not be liable for any loss or damage arising from use of, or reliance on, the material. Nothing in this licence affects the operation of any applicable exception or limitation contained in the Copyright Act 1968. Further information may be obtained by contacting copyright@ga.gov.au ISSN 1448-2177 ISBN 978-1-921498-64-0 Hardcopy ISBN 978-1-921498-63-3 Web GeoCat # 65991 Bibliographic reference: Clark, D., (Editor), 2009. Potential geologic sources of seismic hazard in the Sydney Basin. Proceedings volume of a one day workshop. Geoscience Australia Record 2009/11. 115pp.

  • Seismic Hazard in Sydney Proceedings of the one day workshop

    iii

    Foreword The Sydney Basin encloses a significant proportion of the Australian population, and the 1989 M5.6 Newcastle earthquake demonstrated that the basin is not immune from the impact of even relatively modest earthquakes. In spite of this, few investigations have been conducted to identify and characterise potential geologic sources of strong ground shaking. A recent major study of the southern part of the basin commented that “The available data are less complete than ideal for the purposes of probabilistic seismic hazard analysis”. Essentially, the extreme infrequency of large earthquake events in intraplate regions, such as Australia, means that the short historic record of seismicity is poorly suited to the task of assessing seismic hazard. Hence, geologic, geomorphic and paleoseismic knowledge has a vital role to play in obtaining constraint on the probable location and recurrence of large and damaging earthquakes near Sydney. In April 2005 a one–day workshop at the University of Sydney brought together a diverse range of researchers with experience in the geology and geomorphology of the Sydney Basin, neotectonics and seismic hazard science. A series of seminars were presented covering geology, geomorphology, seismicity and seismic hazard. These served as a nucleation point for subsequent discussion, and the drafting of the papers presented herein. This proceedings volume contains within its covers tools for understanding large earthquake occurrence within the Sydney Basin. Hence, it represents a framework upon which future advances in our understanding of the seismic hazard posed to Australia’s largest population centre may be based.

  • Seismic Hazard in Sydney Proceedings of the one day workshop

    iv

    Contents

    Foreword .....................................................................................................................................................iii Neotectonics and landscape evolution of southeastern Australia: establishing a geologic context for contemporary seismicity QUIGLEY M. C., SANDIFORD M. & CLARK D......................................................................................1 The Inner Sydney Basin: Geology, Land Surface and Earthquakes BRANAGAN D..............................................................................................................................................7 Review of structure and basement control of the Lapstone Structural Complex, Sydney Basin, eastern New South Wales FERGUSSON C. L. ......................................................................................................................................13 Geomorphological evidence for neotectonic activity on the northern Lapstone Structural Complex RAWSON A. & CLARK D.. ........................................................................................................................19 New field observations pertaining to the age and structure of the northern Lapstone Structural Complex, and implications for seismic hazard CLARK D. & RAWSON A. .........................................................................................................................31 Seismicity of the Sydney Basin Region GIBSON G. .................................................................................................................................................46 Notes on the Tectonic setting of, and Attenuation in, the Sydney Basin MCCUE K...................................................................................................................................................58 Observations on faulting in the Sydney area reconciled with the seismicity rates: probabilistic fault rupture recurrence models BERRYMAN K., WEBB T., NICOL A., SMITH W. & STIRLING M...........................................................61 Ground motions in Sydney from an Earthquake on the Lapstone Structure SOMERVILLE P. & GRAVES R..................................................................................................................84 Ground-motion attenuation modelling in southeastern Australia ALLEN T., CUMMINS P. R. & DHU T. ......................................................................................................93 Landslides in the Sydney Basin: Is there a seismic link? TOMKINS K., HUMPHREYS G. S., MACRIS J. & HESSE P. P.................................................................100 Ground movements and seismicity associated with underground coal mining in the Appin area HATHERLY P., HEBBLEWHITE B. & POOLE G......................................................................................109 Workshop Programme..............................................................................................................................114 Participants list .........................................................................................................................................115

  • Seismic Hazard in Sydney Proceedings of the one day workshop

    1

    Neotectonics and landscape evolution of southeastern Australia: establishing a geologic context for contemporary seismicity MARK C. QUIGLEY1, MIKE SANDIFORD1, DAN CLARK2 1SCHOOL OF EARTH SCIENCES, THE UNIVERSITY OF MELBOURNE 2GEOSPATIAL AND EARTH MONITORING DIVISION, GEOSCIENCE AUSTRALIA ABSTRACT Southeastern Australia contains a rich geologic record of Plio-Quaternary reverse faulting and associated landscape evolution that can be used to provide geologic constraints on historical seismicity. The Mt Lofty-Flinders Ranges-eastern Gawler Craton region and Eastern Highlands are characterized by high fault density, “youthful” geomorphology, and high seismic activity relative to most of Australia, including the intervening Murray Basin. Inferred ~east-west directed maximum compressive paleostress orientations derived from Plio-Quaternary faults are generally consistent with ~east-west to ~southeast-northwest maximum compressive stress orientations derived from historical earthquake focal mechanisms, providing a link between the neotectonic record, seismicity, and in situ stress. Plio-Quaternary fault slip rates along range-bounding reverse faults range from 20 to 150 m per million years (m Myr-1). Coupled with slow bedrock erosion rates at range summits, this suggests a minimum of 100 m of surface uplift has occurred over considerable areas of southeastern Australia since the Miocene. Estimates of recurrence interval of large magnitude, surface rupturing earthquakes along individual faults range from ~ 22 000 to ≥ 83 000 years. Single- event fault displacements may have reached up to 8 m in total fault offset. The data acquired from neotectonic investigations bear heavily on the modes, mechanisms, and seismic risk associated with the active regional deformation of southeastern Australia, including the Sydney Basin. INTRODUCTION Although records of historical earthquakes provide cursory information on active crustal deformation and seismic risk, recurrence intervals of large earthquakes in many intracontinental regions commonly surpass the life span of these records by or

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