Australia (AUS)

Authors:

T. Allen, J. Griffin, M. Leonard, D. Clark, H. Ghasemi

Summary

The Global Hazard Mosaic coverage of the Australian continent uses the 2018 model of Geoscience Australia (Allen et al., 2018a and Allen et al., 2018b), with input from greater seismology community in Australia, as an update to the 2012 national model. The model was originally implemented in the OpenQuake (OQ) engine format, and only the computed sites grid was modified by the GEM Secretariat.

Information about the OQ model versions and input files can be found on the Results and Dissemination page.

Interactive Viewer

The viewer below depicts the seismic sources and hazard results in terms of PGA for a return period of 475 years. Click on the menu in the upper right corner to select the layer.

viewer_legend

Tectonic overview

Most of the Australian continent is stable, and seismicity is relatively infrequent though intraplate earthquakes do occur and may be damaging.

The major exception to this is in far northern Australia, where the continental crust is colliding with the microcontinents of Indonesia, particularly in Papua New Guinea. For more information on this region, see Indonesia. Australian territory may also be affected by the interaction of the Australian and Pacific plates to the east in New Zealand.

Basic Datasets

Please refer to Allen et al., 2018a and Allen et al., 2018b.

Hazard Model

Seismic Source Characterisation

The development of the Australian source model is explained by Griffin and Davies, 2018, and the results are summarized by Allen et al. (2018a). A logic tree combining 20 source models from various contributors (all open access, peer-reviewed, and with national coverage) accounts for some epistemic uncertainty; a panel of experts assigned the weighting for each model. Additional epistemic uncertainty was accounted for during the model parameterization.

Together, the source models include:

  • large, background area sources
  • smaller, regional area sources
  • seismotectonic sources consiting of both complex faults and area sources, and
  • smoothed seismicity modelled as point sources

The sources are depicted below in the interactive viewer.

Ground Motion Characterisation

Non_cratonic Weight
Allen2012 0.208
SomervilleEtAl2009NonCratonic 0.205
AtkinsonBoore2006 0.138
BooreEtAl2014 0.166
ChiouYoungs2014 0.13
ChiouYoungs2008 0.153
Cratonic Weight
Allen2012 0.192
SomervilleEtAl2009YilgarnCraton 0.228
AtkinsonBoore2006 0.125
AtkinsonBoore2006Modified2011 0.118
BooreEtAl2014 0.106
ChiouYoungs2014 0.085
ZhaoEtAl2006Asc 0.146
Subduction Weight
Allen2012 0.104
SomervilleEtAl2009NonCratonic 0.099
AtkinsonBoore2006 0.139
AtkinsonBoore2006Modified2011 0.17
BooreEtAl2014 0.125
AbrahamsonEtAl2015SSlab 0.222
AtkinsonBoore2003SSlab 0.141

Results

Hazard curves were computed with the OQ engine for peak ground acceleration (PGA) and spectral acceleration (SA) at 0.2s, 0.5s, 1.0s, and 2s. The computation was performed on a grid of 90521 sites (spaced at approximately 10 km) with reference soil conditions corresponding to a shear wave velocity in the upper 30 meters (Vs30) of 760-800 m/s.

The hazard map for PGA corresponding to a 10% probability of exceedance in 50 years (475 year return period), can be seen using the interactive viewer. For a more comprehensive set of hazard and risk results, please see the GEM Visualization Tools.

References

Allen, T., J. Griffin, M. Leonard, D. Clark, and H. Ghasemi (2018a). The 2018 National Seismic Hazard Assessment for Australia: model overview, Geoscience Australia Record 2018/27, Canberra, doi: 10.11636/Record.2018.027.

Allen, T. I., J. Griffin, and D. Clark (2018b). The 2018 National Seismic Hazard Assessment for Australia: model input files, Geoscience Australia Record 2018/32, Canberra, doi: 10.11636/Record.2018.032.

Griffin, J., & Davies, G. Earthquake sources of the Australian plate margin, Geoscience Australia Record 2018/31, Canberra, doi: 10.11636/Record.2018.031.