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Detailed seismic velocity/depth models of the Upper lithosphere of the Pilbara Craton, Northwest Australia

Created 17/10/2025

Updated 17/10/2025

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Detailed velocity/depth models of the crust of the Pilbara Craton have been produced from amplitude studies of refracted and reflected seismic waves and their travel-times. On three profiles, a near-surface high-velocity layer, in which the velocity sometimes reaches 6.65 km s-1, is interpreted as Hamersley Basin strata overlying the crystalline basement. The seismic velocity in the near-surface crystalline basement is about 6.0 km s-1, and increases with depth through the crust, reaching 6.1-6.2 km s-1 at 11-14 km depth. Below this , at about 15 km depth, a steeper gradient to 6.35-6.45 km s-1 defines an intracrustal seismic boundary. In the lower part of the crust, velocity gradients increase the velocity to 6.6-7.2 km s-1 . In some models, second-order velocity increases with depth are used to explain bright cusps in the data. although these could also be caused by topography on the crust/mantle boundary. The crust/mantle boundary is transitional over 4-5 km, and upper mantle (Pn) velocities range from 7.5 to 8.5 km s-1 . On one profile, a sub-Moho boundary at which the velocity increases from 8.2 to 8.35 km s-1 was recognised 14 km below the crust/mantle boundary. Previously published seismic models of the region show lateral inhomogeneity in the crust of the Capricorn Orogenic Belt, and this complicates a quantitative analysis of the amplitudes of seismic signals recorded in the orogen. However, a qualitative analysis based on the observed amplitudes, the positions of the ray-critical cusps of the previously published models , and the gravity field suggests that , while the intracrustal boundary at about 15 km depth may be sharp, the lower crust in the orogen must have high seismic velocities (and densities) and the crustal thickness in the previous models is probably not an overestimate. Increasing metamorphic grade with depth in the Yilgarn Craton probably ensures positive velocity gradients in the crust in the craton , so that the crustal thickness in the previously published models is considered reasonable. Thus, the interpreted large difference in crustal thickness between the Pilbara Craton (approximately 30 km) and the Yilgarn Craton ( 50 km) is substantiated.

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Field Value
Title Detailed seismic velocity/depth models of the Upper lithosphere of the Pilbara Craton, Northwest Australia
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/2b6d6dcd-29f6-44de-87b9-7dce1d2be62a
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 20/04/2018
Geospatial Coverage
Map data © OpenStreetMap contributors
{
  "coordinates": [
    [
      [
        115.21,
        -27.7
      ],
      [
        121.89,
        -27.7
      ],
      [
        121.89,
        -19.37
      ],
      [
        115.21,
        -19.37
      ],
      [
        115.21,
        -27.7
      ]
    ]
  ],
  "type": "Polygon"
}
Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "Detailed seismic velocity/depth models of the Upper lithosphere of the Pilbara Craton, Northwest Australia". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/detailed-seismic-velocity-depth-models-of-the-upper-lithosphere-of-the-pilbara-craton-northwest