Misfit functionals in Laplace-Fourier domain waveform inversion, with application to wide-angle ocean bottom seismograph data

Rie Kamei, R. Gerhard Pratt, Takeshi Tsuji

    研究成果: Contribution to journalArticle査読

    22 被引用数 (Scopus)

    抄録

    In seismic waveform inversion, non-linearity and non-uniqueness require appropriate strategies. We formulate four types of L2 normed misfit functionals for Laplace-Fourier domain waveform inversion: i) subtraction of complex-valued observed data from complex-valued predicted data (the 'conventional phase-amplitude' residual), ii) a 'conventional phase-only' residual in which amplitude variations are normalized, iii) a 'logarithmic phase-amplitude' residual and finally iv) a 'logarithmic phase-only' residual in which the only imaginary part of the logarithmic residual is used. We evaluate these misfit functionals by using a wide-angle field Ocean Bottom Seismograph (OBS) data set with a maximum offset of 55 km. The conventional phase-amplitude approach is restricted in illumination and delineates only shallow velocity structures. In contrast, the other three misfit functionals retrieve detailed velocity structures with clear lithological boundaries down to the deeper part of the model. We also test the performance of additional phase-amplitude inversions starting from the logarithmic phase-only inversion result. The resulting velocity updates are prominent only in the high-wavenumber components, sharpening the lithological boundaries. We argue that the discrepancies in the behaviours of the misfit functionals are primarily caused by the sensitivities of the model gradient to strong amplitude variations in the data. As the observed data amplitudes are dominated by the near-offset traces, the conventional phase-amplitude inversion primarily updates the shallow structures as a result. In contrast, the other three misfit functionals eliminate the strong dependence on amplitude variation naturally and enhance the depth of illumination. We further suggest that the phase-only inversions are sufficient to obtain robust and reliable velocity structures and the amplitude information is of secondary importance in constraining subsurface velocity models.

    本文言語英語
    ページ(範囲)1054-1074
    ページ数21
    ジャーナルGeophysical Prospecting
    62
    5
    DOI
    出版ステータス出版済み - 1 1 2014

    All Science Journal Classification (ASJC) codes

    • 地球物理学
    • 地球化学および岩石学

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