Scaling and Seismic Reflectivity: Implications of Scaling on Avo

AVO analysis of seismic data is based on the assumption that transitions in the earth consist of jump discontinuities only. The generalization of this type of transition to a more realistic class of transitions shows a drastic change in observed AVO behavior, especially for the large angles currently attained by increasing cable lengths. We propose a simple approach that accounts for this anomalous behavior by renormalizing the observed AVO. This renormalization allows for a separation of the observed AVO effects in terms of a conventional Zoeppritz contribution and a scaling contribution in those cases where the transitions can no longer be considered as isolated jump discontinuities. After renormalization, the inverted fluctuations regain their relative magnitudes which, due to the scaling, may have been significantly distorted. An example of these distortions are tuning effects, often erroneously interpreted as bright spots. INTRODUCTION Observed amplitude-variation-with-offset (AVO) behavior of surface seismic reflection data has led to inferences ranging from the successful identification of hydro-carbon traps (Castagna and Backus, 1993) to the misidentification of AVO anomalies. The reason for this mixed success does not necessarily lie in the data's intricacies but may be caused by oversimplification of the models, and the lack of understanding of both the reflection and propagation characteristics of seismic waves. Recent increases in cable lengths are making these matters even worse. Amongst the various identifiable issues that are responsible, one may mention the current inability to accurately model seismic amplitudes, successfully integrate well and seismic data, and unambiguously interpret AVO.