The reason for this can be seen in Figure 1, which plots the P and S-wave velocities as a function of gas saturation.
To perform a less ambiguous interpretation of our inversion results, we must perform full elastic inversion, in which we estimate P-impedance, S-impedance (the product of density and S-wave velocity) and density. However, these predictions were somewhat ambiguous since P-impedance is sensitive to lithology, fluid and porosity effects, and it is difficult to separate the influence of each effect. Early inversion techniques transformed the seismic data into Pimpedance (the product of density and P-wave velocity), from which we were able to make predictions about lithology and porosity. Seismic inversion is a technique that has been in use by geophysicists for over forty years.