Simulation And Prestack Migration Method For GPR Data In Attenuation Medium

In prestack depth migration using explicit extrapolators, the attenuation of the electromagnetic wave for ground penetrating radar (GPR) has been almost neglected so far. Conventional migration techniques aim at processing common-offset data. This paper presents one kind of migration method for considering absorption effect. The finite difference algorithm in this paper is based on wave equation theory and the character of absorption. After getting simulation result of a model, both phase velocity and absorption coefficient are used in the wave extrapolation in order to take absorption effect into account in the migration method.The finite-difference time-domain (FDTD) scheme for wave field simulation can be derived from the Maxwell' s curl equations. The size of a cell and the interval of time are determined by Courant condition that is a numerical stability condition. In order to eliminate the effects of boundaries, the perfectly matched layer (PML) absorption boundary condition is used in this paper. The absorption effect of the PML boundary is very nice.It is known that it is necessary to consider absorption in GPR by comparing profile properties obtained from absorption-free and middle absorption models. The finite difference wave field extrapolation operator, which contains a functional relation of attenuation and complex velocity, can be derived from wave equations. The inverse operator can be derived from the finite difference wave field extrapolation operator. Finite differential prestack depth migration can be realized using theinverse operator.To show the necessity and effectiveness of taking absorption into account in migration, middle absorption models are used in this paper. The migration in this paper can get the higher lateral resolution and realize absorption compensation. The migration image obtained from the method for compensating absorption is better than others obtained from the methods without considering absorption. The quality and high-resolution information about the near surface media can be more accurately obtained through this migration method that compensates absorption.