(n.) Geophysics. Abbreviation for amplitude variation with offset. Variation in seismicreflection amplitude with change in distance between shotpoint andreceiver that indicates differences in lithology and fluid content in rocks above and below the reflector. AVO analysis is a technique by which geophysicists attempt to determine thickness, porosity, density, velocity, lithology and fluid content of rocks. Successful AVO analysis requires special processing of seismic data and seismic modeling to determinerock properties with a known fluid content. With that knowledge, it is possible to model other types of fluid content. A gas-filled sandstone mightshow increasing amplitude with offset, whereas a coal might show decreasing amplitude with offset. A limitation of AVO analysis using only P-energy is its failure to yield?a unique solution, so AVO results are prone to misinterpretation. One common misinter pretation is the failure to distinguish a gas-filled reservoir from a reservoir having only partial gassaturation ("fizz water"). However, AVO analysis using source-generated or mode-converted shear wave energy allows differentiation of degrees of gas saturation. AVO analysis is more successful in young, poorly consolidatedrocks, such as those in the Gulf of Mexico, than in older, well-cemented sediments. Alt. form: amplitude variation with offset. More Details: Hydrocarbon Detection With AVO; Seismic Inversion: Reading Between the Lines