Séminaire ISTerre

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Full waveform inversion from shallow to deep : the role of reflections and the need for a robust objective function

mercredi 25 octobre 2023 - 10h00

GIUSEPPE PROVENZANO - ISTerre, équipe Ondes
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Full waveform inversion (FWI) iteratively minimizes a chosen measure of the distance between computed and recorded full seismograms (objective function), aiming at a broadband (migration+tomography) reconstruction of the subsurface properties, within a chosen approximation of the wave physics. In surface seismic surveys, however, FWI suffers from the limited penetration depth of the recorded diving waves. Under these circumstances, FWI does not live up to the expectations of a unified migration+tomography method, behaving instead as a least-square migration in a fixed background model. In order to address these limitations, joint inversion of diving and reflected waves (JFWI) introduces explicitly reflections as virtual deep seismic sources in a tomographic objective function, thus enriching the full-waveform kernel with low wavenumbers beyond the depths sampled by refractions. This seminar is going to discuss the principles of JFWI and its contribution to achieving true broadband subsurface models. A graph-space optimal transport JFWI objective function is introduced, along with a reformulation of the problem in pseudo-time domain, to ensure robustness against cycle-skipping. This aims at a waveform-based imaging approach less reliant on the quality of the starting models and thus more widely applicable in realistic limited-aperture, limited-bandwidth datasets for geo-hazards and geo-resources.

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Equipe organisatrice : Organisation labo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères