A damped random boundary condition for prestack reverse time migration

The boundary conditions and storage requirements of reverse time migration (RTM) are often restricted to each other.The selection of these two parameters directly affect the imaging results and application conditions of RTM.Therefore, it is very important to study the boundary conditions and corresponding storage strategies for RTM.We proposed a damped random boundary condition, in which the energy attenuation layer and the random velocity layer were added outside of the real wavefield in turn.This method could effectively reduce the energy interference from random reflection.The inverse operation of the wave equation could reconstruct the source wavefield.Combined with cross-correlation imaging conditions, we conducted the RTM calculation.The results of comparison and analysis show that, compared with the random boundary condition, at the expense of less storage efficiency, the proposed method could obtain a better migration result, and the accuracy is very close to the results obtained by the perfectly matched layer boundary condition.The correctness of the above conclusion is verified by the example of salt model and big offset model.