Application of CFS-PML in complex velocity models

In numerical simulation of seismic wave,the limited space size of discrete grids usually leads to artificial reflections when calculating the outermost layer of the model.The perfectly matched layer (PML) method has achieved good results in absorbing artificial reflections,of which the complex frequency-shifted perfectly matched layer (CFS-PML) is particularly effective.Many studies that discussed the optimal settings of the CFS-PML parameters only consider homogeneous velocity models.However,there are usually complex velocity models with strong heterogeneous in field applications.Therefore,the CFS-PML parameters setting method of complex velocity models is explored based on the setting method of homogeneous velocity models.It is considered that the parameter setting is not only related to the source and grid properties,but also to the velocity of the absorption layer and the wavelength,that is,highly dependent on the velocity model.For a complex velocity model,the key to parameter setting is how to select a reference velocity,and three practical selection methods of reference velocity are given.By testing and comparing the absorption effects of three complex models,i.e.double-layer,multi-layer and Marmousi models, the best reference velocity selection method is defined as the median velocity of boundary medium,and then the setting method of CFS-PML optimization parameters for complex velocity models is proposed. © 2020, Editorial Department OIL GEOPHYSICAL PROSPECTING. All right reserved.