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Imaging the northeast lobe of the Sudbury Structure through 2D and 2.5D visco-acoustic full-waveform inversion
  • Brian Jose Gregorio Villamizar,
  • Gerhard Pratt,
  • Mostafa Naghizadeh
Brian Jose Gregorio Villamizar
University of Western Ontario

Corresponding Author:[email protected]

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Gerhard Pratt
University of Western Ontario
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Mostafa Naghizadeh
Laurentian University
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We conduct two-dimensional (2D) and two-and-one-half dimensional (2.5D) visco-acoustic full-waveform inversion in the frequency domain using new long-offset data from the northeast lobe of the Sudbury structure acquired in 2017. We implement a multiscale inversion strategy based on frequency continuation, and the progressive inclusion of later arrivals, in an effort to mitigate the nonlinearity of the inverse problem. This strategy is equally implemented in both 2D and 2.5D schemes, enabling proper comparisons between their respective results. We start by minimizing logarithmic phase-only residuals, and continue with the minimization of conventional phase-amplitude residuals at later stages, addressing large dynamic variations within our dataset. We demonstrate that the 2.5D modeling technique, which requires more computational resources than its 2D counterpart, is not necessary at this location because the acquisition geometry is only mildly crooked. We illustrate this by analyzing inverted source signatures, time-domain synthetic waveforms, and by performing visual comparisons of the inverted 2D and 2.5D velocity models. We successfully retrieve the velocity structure in the first 1.5 km of the subsurface, and the internal stratigraphic character of the Sudbury Igneous Complex (SIC) is identified within this velocity model. Different velocity domains within our model closely correlate with known geology. This allows us to proceed with a joint analysis of the inverted velocity model and the migrated seismic section of the reflection survey that reveals important structural characteristics of prominent SIC layers, such as their inclination degree and thicknesses, as well as their continuation at depth.