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Separation of Migration and Tomography Modes of Full-Waveform Inversion in the Plane-Wave Domain
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 80th EAGE Conference and Exhibition 2018, Jun 2018, Volume 2018, p.1 - 5
Abstract
Full-waveform inversion (FWI) includes both migration and tomography modes. The migration mode acts like a non-linear least-squares migration, mapping model interfaces with reflections, while the tomography mode builds the background velocity model. The migration mode is the main response of inverting reflections while the tomography mode exists in response to inverting both the reflections and refractions. To emphasize one of the two modes in FWI, especially for inverting reflections, the separation of the two modes in the gradient of FWI is required. Here, we present a new method to achieve this separation with an angle-dependent filtering technique in the plane-wave domain. We first transform the source and residual wavefields into the plane-wave domain with the Fourier transform and then decompose them into the migration and tomography components using the scattering angles between the transformed source and residual plane waves. Scattering angles close to 180° contribute to the tomography component, while the others correspond to the migration component. We found that this approach is very effective and robust even when the medium is relatively complicated with strong lateral heterogeneities, steeply dipping reflectors, and strong seismic anisotropy. This is well demonstrated by theoretical analysis, and numerical tests with synthetic and field datasets.