Amplitude Versus Offset (AVO)
contribution of this second effect is often ascribed to the difference
between Poisson's ratio of the layers. However, the equations
clearly show the cause to be the difference in compressional velocities:
The net result is the same, no matter how it is described. For constant Poisson's ratio above and below a boundary, amplitude decreases with offset. If the upper layer has a higher Poisson's ratio than the lower, positive peaks decrease in amplitude and could go negative, while negative peaks get larger. The reverse takes place when Poisson's ratio contrast is reversed.
are other causes of amplitude versus offset variations:
adequate accounting or control must be given for each of these
effects in order to relate the remaining amplitude variation to
reflectivity changes. Model studies are an essential element in
deciding if these other effects have been properly corrected.
Synthetic seismograms made this way will show the effects of amplitude
versus offset. The conventional synthetic seismogram might tie
the near trace data, but should not be expected to always agree
well with the stacked data or the far trace data.
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