Free-surface Related Multiples Imaging Method Based On Reverse Time Migration

The conventional reverse time migration only uses primary waves to imaging,and the surface multiples are regarded as noise and suppressed.However,the additional underground reflection information provided by the surface multiples can be used for migration imaging,and the imaging range is widened to improve the imaging accuracy.Therefore,based on reverse time migration,a surface multiple and primary reflection combined reverse time migration imaging method is proposed in this paper.It does not need to predict or separate the surface multiple reflection,and can directly imaging the primary and surface multiples.First,in the part of high-precision forward modeling of multiples data,we realized the numerical simulation of seismic wave field based on the conventional grid finite difference method,and got the seismic data containing multiples.The seismic data imaging test of the forward simulation is obtained by using the combined reverse time migration imaging method of surface multiple wave and primary waves.Through the horizontal layered model and complex structure model test,the results show that the proposed method can not only effectively compared with conventional imaging,and primary waves reverse time migration,migration method combined with the proposed inverse can provide additional structural information,based on the imaging section a wave and surface wave combined with multiple reverse time migration accurate imaging of complex structures.On this basis,by changing the migration velocity,we further prove the effect of velocity accuracy on the reverse time migration results,and verify it by different speed models.Among them,based on the model test of reverse time migration surface multiple imaging method,imaging condition is used by the source is the normalized cross-correlation imaging condition better cross-correlation imaging condition,the denoising method,which is based on the Laplasse frequency noise suppression methods,effectively suppress the low frequency noise.According to the boundary conditions,the PML absorption boundary condition is adopted by comparison and analysis.