Golden Grove Mine PSHA

Probabilistic Seismic Hazard Assessment


EMR Golden Grove Pty Ltd


Western Australia


March 2020

Australia/New Zealand

ATC Williams undertook a site-specific Probabilistic Seismic Hazard Assessment (PSHA) to develop a Uniform Hazard Spectrum (UHS) at the bedrock level in accordance with best practice (i.e. ANCOLD, 2019), with annual exceedance probabilities (AEPs) of earthquake return periods.

Apart from ANCOLD 2019, the 2018 National Seismic Hazard Assessment for Australia is also used as a reference for seismic source and Ground Motion models. The results of this assessment were compared with the following two references.

  • The 2012 Australian Earthquake Hazard Map by Leonard et al., 2013
  • The 2018 Australian Earthquake Hazard Map by Geoscience Australia (GA)
  • The time histories of acceleration for the site were selected from the Pacific Earthquake Engineering Center (PEER, Goulet et al., 2019) database based on earthquake magnitude, epicentral distance and the average shear-wave velocity in the upper 30 m (Vs30).

— Features and solutions

There was a significant reduction in the seismic hazard at this site for the 2500 return period in the published hazard map NSHA18 compared to the Hazard map published in 2013 by Geoscience Australia. The key reasons for the decrease in seismic hazard factors from 2012 to 2018 seismic hazard maps are due to:

  • An increase in Gutenberg and Richter (1944) b-values, particularly in eastern Australia, resulted from the ML to MW conversions. This decreases the rates of rare large earthquakes relative to moderate-magnitude earthquakes.
  • The use of modern ground-motion prediction equations (GMM) that do not rely on the PGV to PGA conversions. The recent GMMs also predict faster attenuation of PGA with distance and thus lower ground-motion hazard.
  • A reduction in the rates of moderate-to-large earthquakes (MW ≥ 4.0); due to the correction of pre-1990 local magnitude ML estimates and the conversion of ML to M.
  • To account for epistemic uncertainty, three seismic source models (with varying weightings) have been included in this assessment. The first model is the DIM-AUS (Dimas & Venkatesan, 2016) area source model. The second model is the AUS6 (Dimas & Gibson, 2016) area source model. The third model is the NSHM13 (Leonard et. al., 2012) model made of two layers, a main source zone layer and a background source zone layer. All the models are composed of a series of zones at shallow depths. The fault sources are included from Geoscience Australia’s Neotectonic Faults Database.


  • De-clustered Catalogue – removing dependent events such as foreshocks and aftershocks
  • Deep understanding of geology and tectonic
  • Local Site Effects: when a site is founded on relatively weak deposits, wave propagation analysis should be carried out to estimate the potential amplification of the ground shaking when the waves propagate vertically through the softer soils
  • Time History Analysis: The appropriate time histories selected for dynamic deformation analyses from similar seismotectonic conditions, PGA, earthquake magnitude, epicentral distance and rock conditions

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