Porosity - Lithology From Shear Seismic
The amplitude of each of these components versus incidence angle is shown below. Notice the dramatic change in reflected energy at angles above the critical angle.
If an S-wave reaches the interface, converted S-waves, SPt and SPr, are also created. For seismic surveys, SH is the component of the shear wave (SPr) perpendicular to the vertical plane containing the seismic line. SV is the component in the plane. The direction of particle motion for the various modes is shown below.
When SH is in the interface plane, there is no conversion of SH-waves into P- and SV-waves and inversely. This is why SH seismic records are more simple as a rule than the P or SV records.
Interference from shear waves on conventional CDP seismic stacking is avoided by adequate velocity analysis, since shear waves are much slower than compressional and have much higher normal moveout. The typical velocity regime is shown below.
suitably gathering and velocity filtering seismic traces, the
compressional and shear arrivals can be separated from each other.
The interval velocity from compressional and shear sections can
be computed from the stacking velocity of each. Poisson's ratio
can be computed and displayed from:
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