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通过对该文两个特殊模型的模拟计算可知,尽管各层介质的瑞利波速度相等,但瑞利波还是存在频散现象。波速的变化说明,一定波长的瑞利波波速是一定范围内介质的综合反映;对于瑞利波速相等的两层介质模型而言,其波长深度转换系数并不随覆盖层厚度而变化;对于三层以上的层状介质而言,转换系数随各层介质厚度而变化,且各分界面的转换系数不同,一般浅层界面的转换系数大于深层界面的转换系数,实测结果也验证了该结论。可见,实际工作中采用半波长的解释方法肯定会造成一定的误差。研究适用的非线性反演方法是提高瑞利波勘探解释精度的必要途径。
Through the simulation calculation of two special models, we can see that Rayleigh wave has the phenomenon of frequency dispersion even though the Rayleigh wave velocities are equal in all layers. The change of wave velocity shows that the Rayleigh wave velocity of a certain wavelength is a comprehensive reflection of the medium in a certain range. For the two-layer medium model with the same Rayleigh wave velocity, the wavelength depth conversion coefficient does not change with the thickness of the coating; In the above stratified medium, the conversion coefficient varies with the thickness of each layer, and the conversion coefficients of each interface are different. Generally, the conversion coefficient of the shallow interface is larger than the conversion coefficient of the deep interface. The experimental results also verify this conclusion. Can be seen that the practical use of half-wavelength interpretation of the method will certainly cause some errors. Studying the suitable nonlinear inversion method is the necessary way to improve the precision of Rayleigh exploration and interpretation.