Pre-Stack Time Migration Kirchhoff pre-stack time migration has become the standard for imaging seismic data especially for amplitude versus offset (AVO) processing. It is ideal for imaging datasets which exhibit complex geological structures. It allows time migration to be performed using a laterally varying velocity field – it is assumed that the lateral velocity variations are not strong enough to require depth migration. Spectrum’s Kirchhoff migration algorithm builds travel time tables using a double square root equation which allows for time and space velocity variations. The shifted samples are phase corrected and scaled for distance moved before summation into the correct position. The option to use a curved ray calculation is also available. The result is properly imaged gathers suitable for AVO analysis. Kirchhoff is a flexible migration algorithm and can be implemented in 2D or 3D, pre- or post-stack and in time or depth. It can also be used to interpolate the input data and copes with spatially aliased data. Legacy 30 fold data processed through a PSTM sequence. Data from Spectrum Multi-Client seismic library.