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Joint Full Waveform Inversion of Diving Waves and Reflected Waves for Velocity Model Building
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 77th EAGE Conference and Exhibition - Workshops, Jun 2015, Volume 2015, p.1 - 5
Abstract
At depths where there is no sampling by diving waves, FWI behaves as a least-squares migration of the short-spread reflections, hence providing a reconstruction of the short-scale reflectivity at the expense of the long wavelengths of the velocity. Recently, it has been proposed to modify the FWI formalism such that the long wavelengths of the velocity can be updated from reflected waves using some prior knowledge on the reflectivity and an explicit scale separation between the velocity macro-model and the reflectivity. This scale separation allows one to emphasize the forward-scattering regime in the sensitivity kernel of the FWI, referred to as reflection FWI (RFWI). The drawback of the RFWI is to discard the valuable information on the shallow subsurface carried out by diving waves. A new FWI formalism, referred to as joint FWI (JFWI) is proposed and takes advantage of the long-wavelength information carried out by both diving waves and reflected waves to build a smooth velocity model. This formalism leads to a workflow which iteratively cycles the update of the smooth velocity model by JFWI and the update of the short-scale impedance model by classical FWI of short-spread reflections. Application to a synthetic Valhall model illustrates the performance of JFWI.