On the influence of model parametrization in elastic full waveform tomography

SUMMARY Elastic Full Waveform Tomography (FWT) aims to reduce the misfit between recorded and modelled data, to deduce a very detailed model of elastic material parameters in the underground. The choice of the elastic model parameters to be inverted affects the convergence and quality of the reconst...

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Bibliographic Details
Published in:	Geophysical journal international 2012-10, Vol.191 (1), p.325-345
Main Authors:	Köhn, D., De Nil, D., Kurzmann, A., Przebindowska, A., Bohlen, T.
Format:	Article
Language:	eng
Subjects:	Artefacts Computational seismology Density Inverse theory Inversions Mathematical models Numerical approximations and analysis Parametrization Seismic engineering Seismic phenomena Seismic tomography Wave propagation Waveforms
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Summary:	SUMMARY Elastic Full Waveform Tomography (FWT) aims to reduce the misfit between recorded and modelled data, to deduce a very detailed model of elastic material parameters in the underground. The choice of the elastic model parameters to be inverted affects the convergence and quality of the reconstructed subsurface model. Using the Cross‐Triangle‐Squares (CTS) model three elastic parametrizations, Lamé parameters m1 = [λ, μ, ρ], seismic velocities m2 = [Vp, Vs, ρ] and seismic impedances m3 = [Ip, Is, ρ] for far‐offset reflection seismic acquisition geometries with explosive point sources and free‐surface condition are studied. In each CTS model the three elastic parameters are assigned to three different geometrical objects that are spatially separated. The results of the CTS model study reveal a strong requirement of a sequential frequency inversion from low to high frequencies to reconstruct the density model. Using only high‐frequency data, cross‐talk artefacts have an influence on the quantitative reconstruction of the material parameters, while for a sequential frequency inversion only structural artefacts, representing the boundaries of different model parameters, are present. During the inversion, the Lamé parameters, seismic velocities and impedances could be reconstructed well. However, using the Lamé parametrization ‐artefacts are present in the λ model, while similar artefacts are suppressed when using seismic velocities or impedances. The density inversion shows the largest ambiguity for all parametrizations. However, the artefacts are again more dominant, when using the Lamé parameters and suppressed for seismic velocity and impedance parametrization. The afore mentioned results are confirmed for a geologically more realistic modified Marmousi‐II model. Using a conventional streamer acquisition geometry the P‐velocity, S‐velocity and density models of the subsurface were reconstructed successfully and are compared with the results of the Lamé parameter inversion.
ISSN:	0956-540X 1365-246X