The observation of amplitude variation with offset (AVO) or amplitude variation with angle of incidence (AVA) can give the information of lithology change in the subsurface, which has led to several successful cases of finding oil. AVO or AVA analysis, which is done in common-midpoint (CMP) gathers of un-migrated data often lacks accuracy due to the effects of CMP smearing. It is worth analyzing AVO in common-reflection-point (CRP) gathers after prestack migration.
This paper first introduces the concepts of equivalent offset and common-scatter- point (CSP) gathers, and derives the relationship between equivalent offset and incident angle for one CRP. It then analyzes four reasonable amplitude scaling factors during CSP gathering, applies them to synthetic data and compares the results. The paper also investigates the possibility of analyzing AVO behavior in CSP gathers for horizontal reflectors. Finally, it applies the most suitable factor to real data.
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