Aiming at seismic survey difficulties in complex surface and subsurface areas of South China

seismic migration and imaging techniques are studied.First

migration algorithms are discussed and the methods to calculate travel-time and weighting factor are derived for pre-stack time migration

presenting an idea of calculating asymmetrical travel-time

which can allow Kirchhoff pre-stack time migration directly from rugged topography to match higher lateral changes of velocity.Second

a technique to build an overall velocity model(a technique to integrate shallow

middle and deep velocity into a model)is discussed

resulting in a workflow to build a comprehensive velocity model under a condition of rugged topography.Finally

the continuation operator of Fourier finite difference has been developed for the pre-stack depth migration directly from rugged topography.All the proposed methods have been verified with synthetic and real seismic data.