REVERSE TIME MIGRATION IN VTI MEDIA USING PSEUDO‐ACUSTIC APPROXIMATIONS IN STAGGERED GRID

Leandro Di Bartolo¹

¹ Observatório Nacional

doi:10.20906/CPS/CILAMCE2017-0135

Resumo

Algorithms based on finite-difference method (FDM) using staggered grids are the most successfully applied for seismic modeling. Although the elastic theory can better represent wave propagation than acoustics, a central issue is that it is difficult to estimate all the physical parameters involved in geophysical applications, especially in anisotropic media. Additionally, this schemes demand much more CPU time and memory than acoustic schemes and, in many applications, they presuppose the use of algorithms for decoupling quasi-P and quasi-S modes, e.g., in reverse time migration (RTM). Hence, an acoustic algorithm is preferred to be used in RTM. Recently, it has been proposed equivalent staggered-grid schemes (ESG) to solve the second-order wave equations in terms of only one wavefield, resulting in schemes with lower memory requirement than the ordinary staggered-grid schemes. This paper develops a prestack RTM algorithm using ESG scheme applied to acoustic VTI media. First, the ESG numerical scheme is obtained for forward problem using coupled second-order equations in terms of normal stress components. Second, this algorithm is used to implement reverse time migration algorithms applying the excitation-time imaging condition. The developed algorithm is applied to a synthetic example, a complex model known as Hess VTI model.

Palavras-chave: Reverse time migration; Seismic migration; Staggered grid; Finite difference method; VTI pseudo-acoustic equations