Seismic attribute sensitivity to velocity uncertainty

This paper explores the relationship between velocity uncertainty and AVO-related seismic attributes in a dataset from the Blake Outer Ridge, offshore from Florida and Georgia. From an initial velocity model, several realizations were generated that are perturbations of the original velocity model. Prestack wave-equation migration was applied to the data for each velocity realization. In the migrated CMP gathers, velocity coherence was measured by applying semblance analysis. Also, several seismic attributes were calculated in the migrated CMP gathers, including AVO intercept, AVO gradient, and near far offset stack. Preliminary results from attribute versus velocity coherence crossplots at the range of CMPs studied suggest that, for the case of maximum semblance coherence measurements, attribute values are more dispersed for lower coherence values and more localized for higher coherence values. These results are not definitive, and further work is needed to improve the velocity coherence measures.