NMO for several layers with arbitrary dips
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Series | Investigations in Geophysics |
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Author | Öz Yilmaz |
DOI | http://dx.doi.org/10.1190/1.9781560801580 |
ISBN | ISBN 978-1-56080-094-1 |
Store | SEG Online Store |
Figure 3.1-15 shows a 2-D subsurface geometry that is composed of a number of layers, each with an arbitrary dip. We want to compute the traveltime from source location S to depth point D, then back to receiver location G, which is associated with midpoint M. Note that the CMP ray from midpoint M hits the dipping interface at normal incidence at D′, which is not the same as D. The zero-offset time is the two-way time along the raypath from M to D′.

[1] derived the expression for traveltime t along SDG as
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where the NMO velocity is given by
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The angles α and β are defined in Figure 3.1-15. For a single dipping layer, equation (13) reduces to equation (8). Moreover, for a horizontally stratified earth, equation (13) reduces to equation (4). As long as the dips are gentle and the spread is small, the traveltime equation is approximately represented by a hyperbola (equation 5), and the velocity required for NMO correction is approximately the rms velocity function (equation 4).
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See also
- NMO for a flat reflector
- NMO in a horizontally stratified earth
- Fourth-order moveout
- NMO stretching
- NMO for a dipping reflector
- Moveout velocity versus stacking velocity
- Exercises
- Topics in moveout and statics corrections