地震数值计算中台阶状倾斜地层效应的消除

THE ELIMINATION OF EFFECTS OF STEP-SHAPED SLOPES IN SEISMIC NUMERICAL SIMULATIONS

为了消除采用矩形网格的地震波正演计算中,台阶状倾斜界面引发的绕射波和网状干扰波,Zeng提出网格细分加权平滑方法。本文对该方法中加权函数的性质和参数的求取进行了讨论,给出了加权函数的图形和参数选取的办法。规格化因子C可以通过非规格化的加权函数计算。根据需要,定义了表征加权函数平滑度的参数s。由确定的网格大小与s计算衰减因子σ,就可以确定加权函数。对于含有一个倾斜界面的模型进行了数值模拟。一般情形下,参数s必须大于或等于0.2。通过对不同倾角倾斜界面的数值计算,显示了相同参数选择对于地层倾角变化的适应性。

In 1996, Zeng brought a method forward for eliminating the netlike diffractive and interferential wave caused by step - shaped slopes when rectangular meshes were used in seismic numerical simulations. This method uses a weighted function to smooth the slope boundary between two layers. This paper discusses the properties of the weighted function, the method to get relative parameters for the weighted function, and the function＇s figure with respect to some different parameters. The normalized factor C can be obtained from the non - normalized weighted function. As required, this paper defines the parameter s that denotes the smoothness of the weighted function. The attenuation factor a can be determined from the cell size of the mesh and s, and then the weighted function can be determined. In this paper, a numerical simulation for a model with only one slope is realized. As a rule, the parameter s can be 0.2 or larger than 0.2. Some numerical simulations for slopes with different angles show the applicability of the same parameter choice for the variation of slope＇s angles.