边界吸收中镶边法的评价

Evaluation of the bordering methods of the absorbing boundary condition

以均匀层状带凹陷特征的介质模型为例,分析镶边法在常规边界吸收问题中的独到优越性;采用均匀倾斜模型数值实例,详细探讨外侧镶边法在边界吸收中的弊端及其成因.综合数值试算分析表明,外侧镶边法会引入虚假反射波,其原因是边界处速度延拓产生了人为绕射点.提出了内侧镶边方法,即以牺牲局部有效波场来提高数值计算精度、信噪比和可信度,实例验证该方法正确可行.

By taking an isotropic layered medium model with depressed characteristic as example, we analyzed the advantages of the bordering method in solving conventional boundary absorbing problems. By taking a numerical example of an isotropic tilt model, we discussed the drawbacks of the outside bordering method and the origins of the boundary absorption in detail. The generalized numerical analyses show that the outside bordering method could introduce bogus reflected waves, and the reason was that the velocity continuation on the boundary brought in man-made diffraction points. The inside bordering method is proposed for the purpose of improving numerical simulation precision, signal-to-noise ratio, and credibility at the cost of regional effective wave field. The example illustrates that the proposed method is reliable and workable.