瑞利波泄漏模式的模拟研究

Forward Modeling of Rayleigh Leaky Mode Waves

瑞利导波相速度频散曲线有时会出现截止或截断现象,此时必须考虑泄漏模式波的存在,如何快速求取泄漏模式波的相速度大小是研究的核心问题.采用添加附加层的方法,使瑞利波实频散方程求根的范围包含所有的层速度区域,从而可用Abo-zena,Menke和BixingZhang等学者研究过的传递矩阵理论,利用二分法求解相速度大小,即用导波来模拟计算泄漏模式波相速度大小.从模拟计算结果来看,附加层法不仅能模拟出原模型的实数导波,而且还能计算出泄漏模式波的变化.由此可见,用附加层法来计算瑞利波的泄漏模式是可行的;同时,若将该方法应用于瑞利波勘探的反演,它不会增加未知数的个数.

The dispersion curve of the Rayleigh guided waves has the phenomena of cut-off or truncation under some conditions, which contradicts Rayleigh wave exploration. For this problem, in our opinion, we should consider the leaky modes of Rayleigh waves. This paper presented a method to rapidly solve the leaky modes of Rayleigh waves. The method is to append an appropriate layer under the model, so that the solving velocity range can include all layers＇ Rayleigh wave velocities. We calculated the phase velocities of the Rayleigh guided waves in transmission matrix approach in these conditions, namely, we solved the dispersion equation in the bisect-method. Moreover, we also calculated the Rayleigh leaky mode waves of seven models. The results show that the appending layer method can calculate not only the guided waves, but also the leaky mode waves. At the same time, the number of unknown parameters did not change when the method was used in inversion.