The Study Of Varying Grid Reverse Time Migration

The finite difference reverse time migration numerical simulation method is the most commonly used method,which contains abundant seismic information,and is easy to implement in the algorithm.Usually,in order to get high precision simulation results,the sampling grid spacing will be reduced,but this will greatly increase the storage space and reduce the efficiency of computation time and demand.This paper starts from the high order accuracy of the acoustic wave equation based on forward theory and introduces the basic formula of numerical simulation of variable grid offset without interpolation and inverse derivation,the numerical dispersion,and stability conditions etc.By taking the perfectly matched layer boundary condition as the boundary condition of the inverse offset variable grid,it completely absorbed the boundary reflection in the boundary regional.In order to improve the computational efficiency and reduce the storage space,the author has,based on the previous research,improved variable grid algorithm which does not need interpolation in the variable mesh transition zone and requires no smoothing function to smooth.It is regarded as an effective improvement to the variable offset algorithm of traditional grid inverse interpolation.Such grid computing assumes higher efficiency than the conventional one and often the algorithm can save storage space compared to the grid.In order to verify the accuracy of the method,the author has designed six geological models to test the algorithm to verify the adaptability of the model.Analyzing from the numerical simulation accuracy,computational efficiency,and the analysis of storage requirement respectively,we can reach to the conclusion that compared with the conventional grid reverse time migration,the variable grid reverse time migration has a more significant advantage.