In recent years, elastic inversion and quantitative interpretation of pre-stack seismic data have become standard procedures in the petroleum industry. In this presentation, Per Avseth (Norwegian University of Science and Technology) compares extended elastic impedance trends at different chi angles, with rock physics template models. He demonstrates that the elastic impedance attribute does not always comply with the complexity and non-linearity of rock physics models related to geological processes. He also shows how one can honour the non-linearity of a rock physics model and create pseudo-elastic impedance as a function of deviation away from a curved water-wet rock physics model itself (CPEI). Finally, Per demonstrates the use of this approach on seismic inversion data from a selected area in the Mid Norwegian Sea, by mapping of lithology and fluid anomalies that are consistent with rigorous rock physics models.