Kinematic artifacts in the extended subsurface offset domain

We provide a kinematic analysis of the prestack image behaviour in the subsurface offset domain. When the medium properties are perfectly known, the image is expected to focus at the zero subsurface offset, where the incident and the scattering wavefields interact at a common point. However, kinematic artifacts are often observed in subsurface offset common-image gathers (CIGs) away from the zero offset trace, and artificially impairs the expected focusing. These artifacts emerge in relation with the acquisition geometry truncation at the boundaries of the seismic survey extent. We suggest a formation mechanism for the artifacts emergence by considering seismic migration as a superposition of subsurface offset extended impulse responses, contributed by individual data traces. The accumulation of the image, in a trace-by-trace manner, gives an insight to its fundamental building blocks that better explains the formation of the kinematic artifacts. We also discuss the defocusing of the subsurface offset image due to an erroneous migration velocity. In such case, the kinematic artifacts are formed by the same mechanism, while interfering with the essential defocusing information of the image away from the zero offset trace.