2014-09-182014-09-182014-02-28PAIXÃO, Marcelo Tavares. Análise do efeito da discretização do modelo de velocidades nas migrações Kirchhoff e Kirchhoff-Gaussian-Beam 2D pré-empilhamento em profundidade. 2014. 74 f. Dissertação (Mestrado) - Universidade Federal do Pará, Instituto de Geociências, Belém, 2014. Programa de Pós-Graduação em Geofísica.https://repositorio.ufpa.br/handle/2011/5749The Gaussian Beam (GB) is an asymptotic solution of the elastodynamic equation in the paraxial vicinity of a central ray, which approaches better the wave field than the standard zero-order ray theory. The GB regularity in the description of the wave field, as well as its high accuracy in some singular regions of the propagation medium, provide a strong alternative to solve seismic modeling and imaging problems. In this dissertation , I present a new procedure for pre-stack depth migration with true-amplitude, combining the flexibility and robustness of Kirchhoff migration type using superposition of Gaussian beams to represent the wave field. The proposed migration algorithm comprises in two stacking process: the first is the beam stack applied to subsets of seismic data multiplied by a weight function defined such that stack operator has the same formulation of the integral of the Gaussian beams superposition; the second is a weighted diffraction stack by means of the Kirchhoff type integral having as input the stacked data. For these reasons it is called Kirchhoff-Gaussian-Beam (KGB) migration. In order to compare the Kirchhoff and KGB methods with respect to the sensibility on relation to the discretization length, we apply them to the well-know 2D Marmousi dataset using four velocity grids, i.e. 60 m, 80 m, 100 m e 150 m. As result we have that both methods present a much better image for smaller discretization interval of the velocity grid. The amplitude spectrum of the migrated sections provide us with the spatial frequency contents of the obtained image sections.porAcesso AbertoProcessamento sísmicoImageamento sísmicoMigração pré-empilhamentoMigração em profundidadeTeoria do raioFeixes GaussianosDissertaçãoCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOFISICA::SISMOLOGIA