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<abstract>
<title>Kinematic determination of Vp/Vs in multicomponent seismic
Data</title>
<author>Christopher Osareni Ogiesoba and Robert R. Stewart</author>
<p>This paper discusses a method of determining the zero-offset velocity
ratio V<sub>P</sub>/S<sub>S</sub> (&gamma;<sub>0</sub>) via velocity
analysis, using Thomsen's (1999) non-hyperbolic traveltime
equation.  Processing of synthetic shot gathers from a four-layer
geologic model provides the P-wave velocities (V<sub>P</sub>) and PS
velocities (V<sub>S</sub>) used to stack the data sets. A semblance
program written in Matlab code to compute semblance in 3-dimention is
employed to scan for depth varying &gamma;<sub>0</sub>. It was
observed that post-critical angle reflected events adversely affect
the V<sub>P</sub>/V<sub>S</sub> values determined by this
method. Thus, it is necessary to mute the data prior to velocity
analysis. Accuracy increases as the depths to reflecting horizons
increase. This is probably because the conversion point moves closer
towards the midpoint with increasing depth. Furthermore, accuracy
increases by decreasing the sampling interval in each variable used in
the computation of semblance. That is increasing the number of samples
in each variable. This however, linearly increases the computational
cost. By converting the &gamma;<sub>0</sub> and the PS zero-offset
times to the corresponding P-wave times, the correlation of P-wave and
PS stacked sections can be implemented. Correlation of the transformed
PS data and the P-wave stacked data sets is found to be good (the
difference being less than 5%).
</p>
</abstract>
