dc.contributor.advisor TSvankin, I. D. dc.contributor.author Pattnaik, Sonali dc.date.accessioned 2017-07-20T19:38:24Z dc.date.accessioned 2022-02-03T13:01:26Z dc.date.available 2017-07-20T19:38:24Z dc.date.available 2022-02-03T13:01:26Z dc.date.issued 2017 dc.identifier Pattnaik_mines_0052N_11293.pdf dc.identifier T 8309 dc.identifier.uri https://hdl.handle.net/11124/171144 dc.description Includes bibliographical references. dc.description 2017 Summer. dc.description.abstract With the recent advances in seismic data acquisition, such as wide-azimuth, long-offset surveys and low-frequency sources, full-waveform inversion (FWI) has become an efficient tool in building high-resolution subsurface models. Conventional FWI relies mainly on diving waves to update the low-wavenumber components of the background model. However, such FWI algorithms may fail to provide a satisfactory model update for regions probed primarily by reflected waves. This typically occurs for deep target zones where the conventional FWI updates mostly the high-wavenumber model components due to the absence of diving waves. Reflection waveform inversion (RWI) has been developed to retrieve the intermediate-to-long wavelength model components in those deeper regions from reflection energy. In this thesis, I highlight the limitations of conventional waveform inversion when applied to reflections-dominated seismic data and propose a new implementation of RWI for acoustic VTI (transversely isotropic with a vertical symmetry axis) media. I extend the idea of scale separation between the background and perturbation models to VTI media and use an optimized parameterization to mitigate parameter trade-offs in RWI. The proposed workflow repeatedly alternates between updating the long-wavelength model components by fixing the perturbation model and the shorter-wavelength, migration-based reflectivity update. I develop an hierarchical two-stage approach that operates with the P-wave zero-dip normal-moveout velocity $V_{\rm nmo}$ and anisotropy coefficients $\delta$ and $\eta$. At the first stage, $V_{\rm nmo}$ is estimated by applying the Born approximation to a perturbation model in $\delta$ to compute the corresponding reflection data. Although the algorithm does not invert for $\delta$, this parameter helps improve the amplitude fit for the employed acoustic model that ignores the elastic nature of the subsurface. At the second stage, the parameter $\eta$, which can be constrained by far-offset data, is estimated from the obtained perturbation model in $V_{\rm nmo}$. The proposed 2D algorithm is tested on a horizontally layered VTI medium and the VTI Marmousi model. Application of a temporal correlation-based objective function significantly improves recovery of the long-wavelength $\eta$-component, as demonstrated on the Marmousi model. dc.format.medium born digital dc.format.medium masters theses dc.language English dc.language.iso eng dc.publisher Colorado School of Mines. Arthur Lakes Library dc.relation.ispartof 2017 - Mines Theses & Dissertations dc.rights Copyright of the original work is retained by the author. dc.title Full waveform inversion with reflected waves for acoustic 2D VTI media dc.type Text dc.contributor.committeemember Snieder, Roel, 1958- dc.contributor.committeemember Trainor-Guitton, Whitney dc.contributor.committeemember Martin, P. A. thesis.degree.name Master of Science (M.S.) thesis.degree.level Masters thesis.degree.discipline Geophysics thesis.degree.grantor Colorado School of Mines
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