1887

Abstract

Summary

In land applications, topography may impact the imaging if not taken into account. With low-frequency and wide-aperture data, the long-to-intermediate wavelength components of the velocity model can be recovered by full-waveform inversion. Standard static corrections to handle the topography do not work satisfactorily on long-offset data. We present a method to handle 3-D free-surface topography for acoustic FWI by directly modelling the effect of the topography with an immersed-boundary finite-difference scheme. The numerical scheme is aimed specifically at first-order wave equations discretized on standard staggered grids, using high-order derivative operators that are modified based on their relative position to the free surface. We extend the approach to VTI media to be able to model velocity anisotropy required in long-offset inversions. We then investigate the topography artefacts seen on real land full-waveform inversions in relatively simple synthetic experiments, allowing us to quantify the effect of elevation variation on the inversion accuracy. The experiments demonstrate that elevation variations in the order of 1/4 wavelength or somewhat smaller can already create artefacts in the inversion results if ignored.

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/content/papers/10.3997/2214-4609.201700503
2017-06-12
2024-03-29
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References

  1. Alkhalifah, T., Fomel, S. and Biondi, B.
    [2001] The space-time domain: theory and modelling for anisotropic media. Geophysical Journal International, 144(1), 105–113.
    [Google Scholar]
  2. Bohlen, T. and Saenger, E.H.
    [2006] Accuracy of heterogeneous staggered-grid finite-difference modeling of Rayleigh waves. Geophysics, 71, 109–115.
    [Google Scholar]
  3. Huiskes, M.J., Plessix, R.É. and Mulder, W.A.
    [2016] A Fast 3-D Free-surface Topography Method for Acoustic Full-waveform Inversion. In: 78th EAGE Conference and Exhibition 2016-Workshops.
    [Google Scholar]
  4. Lombard, B., Piraux, J., Gélis, C. and Virieux, J.
    [2008] Free and smooth boundaries in 2-D finite-difference schemes for transient elastic waves. 172(1), 252–261.
    [Google Scholar]
  5. Mulder, W.A. and Huiskes, M.J.
    [2017] A simple finite-difference scheme for handling topography with the first-order wave equation. Geophysical Journal International, to appear.
    [Google Scholar]
  6. Plessix, R.É. and Cao, Q.
    [2011] A parametrization study for surface seismic full waveform inversion in an acoustic vertical transversely isotropic medium. Geophysical Journal International, 185(1), 539–556.
    [Google Scholar]
  7. Rodrigues, D. and Mora, P.
    [1993] An efficient implementation of the free surface boundary condition in 2-D and 3-D elastic cases. In: SEG Technical Program Expanded Abstracts. 215–217.
    [Google Scholar]
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