One-way Wave Equation Preserved-amplitude Migration And Imaging In Angles Domain

The traditional method of wave-equation prestack depth migration decomposes full acoustic wave equation into simple one-way equation under the assumption that the velocity field is homogeneous to continue upward wavefield and downward wavefield downwards. This one-way wave equation is accurate in kinematics and can satisfy structural imaging. But it ignores that amplitudes of seismic waves can be reconstructed by the parameters variation of media. And it only has the ability to preserve amplitudes relatively and cannot describe the dynamics characteristics of seismic wave's propagation exactly. In this paper, the approximation of one-way wave equation which describes the kinetic character in complex medium is discussed and derived in detail with the physical meaning and the amplitude fidelity of each term. The paper gives the exact definition of true amplitude migration. Based on the definition, we modify ground boundary conditions used in the traditional method of wave equation prestack depth migration which eliminates the affect from cosine inclination factor. And we apply imaging condition for acoustic pressure reflectivity involved which makes migrated amplitudes reflect the variation of subsurface acoustic pressure reflectivity.Wave equation prestack depth migration based on double-square-root (DSR) equation is another wave equation migration method used widely. It has such advantages as less aliasing, simple boundary process, needless to derive source wavelet and high computation efficiency. In the paper, beginning with the operator of preserved single-square-root equation, we derive preserved amplitude one-way wave equation defined by DSR equation, based on the equivalence between the both with cross correlation imaging condition.The use of imaging amplitude of seismic migration to provide reliable rock parameters and reservoir information for AVO-AVA analysis has become an inevitable trend of the development of seismic exploration technique. Wave equation true amplitude migration technique has the ability to provide exact structural imaging and reflection coefficient information related to angles of sursurface interface. In the paper, we first discuss the multi-arrival phenomenon of both shot domain common imaging gathers (SDCIGs) and offset domain common imaging gathers (ODCIGs) in the medium with strong lateral velocity variation, and point out that angle domain common imaging gathers (ADCIGs) has the ability of selfadaption. With migration based on double square root (DSR) equation and sigle square root (SSR) equation, we output angle domain common imaging gathers. The paper proves how to output true amplitude common refletion angle gathers from shot domain one-way true amplitude migration. And in common reflection angles true amplitude migration multiplication imaging condition is adopted which avoids numerical destabilization of shot domain true amplitude migration.The trial results for the theoretical model data and the real seismic data confirm the correctness of the theory and the practical algorithms of the true amplitude wave equation migration.