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Moveout Approximation for Converted Waves in Layered Orthorhombic Medium
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 76th EAGE Conference and Exhibition 2014, Jun 2014, Volume 2014, p.1 - 5
Abstract
In this work we study the hyperbolic moveout approximations for shear and converted waves in a layered orthorhombic medium with flat interfaces in the horizontal plane of symmetry, distinguishing two types of conversion - PS1 and PS2, with different shear polarizations. Note that the azimuthally dependent NMO velocity function for shear or converted waves is similar to that of compression waves - only the coefficients are different. Given a package of orthorhombic layers with different parameters, one can establish an equivalent effective model consisting of a single layer with the same vertical time as the original package, described by the fast and slow effective NMO velocities, the effective azimuth of the slow velocity, and the vertical compression velocity. The latter is normally obtained from non-seismic information such as check-shot or well logs. Note that the effective azimuths are different for models describing PP, PS1 and PS2 waves.