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Continued progress in acquiring and processing high-quality multicomponent data has provided clear evidence of the influence of anisotropy on reflection traveltimes and moveout inversion. In particular, conventional isotropic imaging methods routinely produce depth misties between PP and PS (converted-wave) sections (e.g., Nolte et al., 2000), which can be removed by joint anisotropic velocity analysis of PP and PS data volumes. In this chapter, PP-wave reflection moveout is combined with traveltimes of mode-converted (PS) and shear (SS) waves in parameter estimation for transversely isotropic media.

We begin by examining joint inversion of PP and PS (PSV) data for the simple model of a horizontal VTI layer. Although the addition of PS traveltimes makes it possible to obtain the ratio of the vertical velocities of P- and S-waves and the shear-wave NMO velocity, inversion for the Thomsen parameters and reflector depth remains nonunique, even for uncommonly large spreadlength-to-depth ratios. Reconstruction of the depth scale of horizontally layered VTI models from surface data requires generation of shear waves and recording of wide-angle SS reflections, as demonstrated by Tsvankin and Thomsen (1995). In the second section we extend P-wave stacking-velocity inversion (tomography) described in Chapter 2 to the combination of NMO ellipses, zero-offset traveltimes, and reflection time slopes of PP- and SS-waves (SS traveltimes can be computed from PP and PS data). Application of the inversion algorithm to a homogeneous TI layer above a dipping reflector shows that for a range of dips and tilt angles of the symmetry axis conventional-spread

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