123 QUAL I TÉ GÉOPHYSIQUEAPPLIQUÉE 5 Full waveform inversion 7 H. Chauris 5.1 Overview Full Waveform Inversion (FWI) is a processing technique to derive quantitative images of the subsurface from seismic measurements. By quantitative, we mean for example P-wave velocity models expressed in m/s, and not only a structural image of the Earth as a classical stack section would provide. The principle is simple: the optimal model is the one for which the computed shot gathers are reproducing the observed shot data. More details on the formulation are provided in section 5.3. Beyond the apparent simplicity, the practical applicability of FWI is a difficult task. This is a non-linear process; the user should provide an initial model; the quality of the final inverted model depends on the reliability of the low frequency content of the observed data. A proper strategy should be established to iteratively determine the model (typically by successively introducing higher frequencies). One also needs to use the adequate wave equation to generate synthetic wave fields and associated This chapter of Seismic Imaging: a practical approach is published under Open Source Creative Commons License CC-BY-NC-ND allowing non-commercial use, distribution, reproduction of the text, via any medium, provided the source is cited. © EDP Sciences, 2019 DOI: 10.1051/978-2-7598-2351-2.c007
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