超吸收边界条件在地质雷达剖面正演中的应用

Application of Super Absorption Boundary Condition in Forward Modeling of Ground Penetrating Radar

运用时域有限差分法正演地质雷达剖面时，边界条件的吸收特性对计算结果起着关键性作用．为了使截断边界的影响尽可能小，对边界条件的吸收特性进行了研究，提出了超吸收技术，让电场与磁场分量同时参与边界条件的计算，采用误差抵消的原理，首先减小截断边界对磁场分量的畸变，进而以此比较精确的磁场值重新计算边界上的电场，从而得到更加精确的电磁场值．数值试验表明，它能有效地减小截断边界的伪反射，提高计算精度．把这一技术用于地质雷达剖面的正演合成，得到了满意结果．

Absorbing boundary condition(ABC) plays a critical role in forward modeling of ground penetrating radar using FDTD (finite difference time domain) method. To decrease the reflection of boundaries and improve the accuracy of modeling result, an algorighm called super absorption technique in which the absorbing boundary conditions are applied to both magnetic and electric fields is proposed. The reflection error of the calculated magnetic field at the boundary using an ABC is related to that of using normal FDTD formula, so it can be significantly reduced through further calculations by applying this value to the computation of the electric field. Thus the more accurate result of electromagnetic is obtained. The numerical test proves that the application of super absorbing boundary conditions can decrease the pseudo reflection of truncating boundaries effectively. The examples of forward modeling of ground penetrating radar profile show that it is better than using other types of boundary conditions.