Assuming the SEG (Society of Exploration Geophysics) polarity standard is followed, there are some cases in which reflections on the compressional (P-P) and converted-wave (P-S) sections show opposite polarities. This situation makes the correlation and interpretation processes more difficult.
To find conditions that relate polarity to elastic parameters, I derived a new approximation for the P-S reflection coefficient (RPS) and also modelled seismic responses from a wide range of geologically plausible interfaces using acoustic P- and S-wave velocities and densities. In also investigate the polarity consistency with offset and how missing velocity or density well-logs used to create synthetic shot-gathers and stacks affect the interpretation process.
As a side result, I show that, with small changes, the new RPS approximation is suitable for AVO (amplitude variation with offset) studies and also describe a more accurate way of computing the theoretical AVO attributes.
Opposite polarities on P-P and P-S sections were found to be associated with situations where not all the rock parameters change in the same direction (e.g. velocities increase and density decreases) across the interface.
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