Analysis of RTM extended images for VTI media

Analysis of RTM extended images for VTI media

Vladimir Li, Ilya Tsvankin and Tariq Alkhalifah, "Analysis of RTM extended images for VTI media", Geophysics 81 (2016): S139-S150. doi: 10.1190/geo2015-0384.1​​​​
BibTeX​ 
Vladimir Li, Ilya Tsvankin, Tariq Alkhalifah
anisotropy, imaging, VTI, wave equation, reverse time migration
2016
​Extended images obtained from reverse time migration (RTM) contain information about the accuracy of the velocity field and subsurface illumination at different incidence angles. Here, we evaluate the influence of errors in the anisotropy parameters on the shape of the residual moveout (RMO) in P-wave RTM extended images for VTI (transversely isotropic with a vertical symmetry axis) media. Using the actual spatial distribution of the zero-dip NMO velocity (VnmoVnmo), which could be approximately estimated by conventional techniques, we analyze the extended images obtained with distorted fields of the parameters ηη and δδ. Differential semblance optimization (DSO) and stack-power estimates are employed to study the sensitivity of focusing to the anisotropy parameters. We also build angle gathers to facilitate interpretation of the shape of RMO in the extended images. The results show that the signature of ηη is dip-dependent, whereas errors in δδ cause defocusing only if that parameter is laterally varying. Hence, earlier results regarding the influence of ηη and δδ on reflection moveout and migration velocity analysis remain generally valid in the extended image space for complex media. The dependence of RMO on errors in the anisotropy parameters provides essential insights for anisotropic wavefield tomography using extended images.​
(print): 0016-8033 (online): 1942-2156