Abstract
For converted waves, stacking as well as AVO analysis requires a true
common reflection point gather which, in this case, is also a common
conversion point (CCP) gather. The coordinates of the conversion
points for PS or SP waves, in a single homogeneous layer can be calculated
exactly as a function of the offset, the reflector depth and the
ratio vp/vs. An approximation of the conversion point on a dipping
interface as well as for a stack of parallel dipping layers is given.
Numerical tests show that the approximation can be used for offsets
smaller than the depth of the reflector under consideration.The traveltime
of converted waves in horizontal layers can be expanded into a power
series. For small offsets a two-term truncation of the series yields
a good approximation. This approximation can also be used in the
case of dipping reflectors if a correction is applied to the traveltimes.
This correction can be calculated from the approximated conversion
point coordinates.
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