To improve seismic wave reverse-time migration (RTM) quality of complex structures,a new RTM imaging condition is shown. Take 2D model as example,one-way wave field and formation reflection angle with Poynting vector are obtained. Correlation calculation between up-way and down-way wave field,and between left-way and right-way wave field of shot and receiver are made, which removes migration noise components. Further,it introduces weight of cosine function of reflection angle into cross-correlation RTM imaging condition to suppress noise. Model study shows that main cause of migration noise is cross-correlation image of different shot and receiver point propagating direction wave field. Cross-correlation image of same shot and receiver point propagating direction wave field can suppress migration noise effectively and maintain imaging ability on sharp angle layer and horizontal surface as well. Imaging results can be further improved with weight of cosine function. Practical seismic data verify the method. In summary,the imaging condition provides an important method guide for improving imaging quality in complex structure area.

We introduce figure repair technology based on partial differential equation into seismic data digital processing, and put forward seismic data repair technology based on diffusion filtering method. The technology diffuses undamaged area's data to data to be repaired using diffusion filtering method with a certain diffusion function. In each iteration, only the data to be repaired is updated, and undamaged area' s data is remained unchanged. Final iteration termination condition can be ensured by comparing difference with threshold before and after iterations. Two application examples of seismic data interpolation processing and seismic data local repair processing show that the technology can achieve the purpose of repairing seismic data. It recovers effectively lost seismic wave field information. Therefore, it can be used in practical seismic data digital processing.

From PM equation we derive muhi-dimensionay diffusion filtering equation discrete formula and its stable condition. We construct multi-scale decomposition and reconstruction method based on diffusion filtering, and provide two specific implementation plans. Application in practical seismic data shows that the method is reasonable and reliable. In the first plan 2D Fourier wave-number spectrum main energy is away from spectrum center with increase of scale, and residual signal acts at high wave numbers, which shows perfect application in random noise suppression. In the second plan 2D Fourier wave-number spectrum energy is close to spectrum center with increase of scale, and residual signal acts at low wave numbers, which shows perfect application in low-frequency reverse time migration noise suppression. The method computation is simple and easy to implement. It provides a multi-scale decomposition and reconstruction method for signal processing. It may has great application in seismic signal processing.

We present an equivalent dual elastic wave separation equation, which simulates particle-velocity, pressure, divergence and curl fields in pure P- and S- modes. The method is used in full elastic wave numerical simulations. We give complete derivations of explicit high-order staggered-grid finite difference discrete equations, together with stability condition, dispersion relation and perfectly matched layer (PML) absorbing boundary condition. Theoretical analysis and numerical simulations show that pare P-waves and S-waves in final numerical results are completely separated in the method. Effect of absorbing boundary is perfect. Storage and computing time requirements are greatly reduced compared with previous works.

We propose an equivalent first-order hyperbolic velocity-stress Biot two-phase isotropic medium elastic wave equation in order to separate pure fast and slow compress waves and pure shear wave in full wave field of two-phase medium.Feasibility of the method is demonstrated with divergence and curl theory.In a high-order staggered-grid finite-difference scheme forward simulating operator is constructed.PML absorbing boundary condition and stability condition are derived.Isotropic and heterogeneous layered two-phase medium models are tested.Full elastic wave field,completely separated pure compress wave and pure shear wave of the solid fluid phase components are obtained.Boundary absorbing effect is perfect,and numerical precision is high.It shows that the fast compress wave and slow compress wave are coupled which can't be separated.They belong to pure compress wave fields.Energy of slow compress wave in fluid phase is greater than that in solid phase which is important in understanding propagating laws and validating elastic wave theory for two-phase medium.