Normal Modes Computation by Generalized Reflection‐Transmission Coefficients Method in Planar Layered Half Space

A new approach is presented to calculate the dispersion curves and normal mode solutions of multilayered solid earth model with low velocity layers based on the generalized reflection‐transmission coefficient method. It is efficient to tackle these two problems by utilizing the single top‐layer secular function proposed by Chen in 1993. However, it is difficult to obtain the lower modes by merely using the single top‐layer secular function due to numerical singularity while the earth model contains low velocity layers. In this paper, we proposed using the secular function set, instead of the single secular function, to solve this problem. With secular function set, different modes can be calculated respectively through corresponding secular function. Numerical experiments show that the new approach is efficient, stable and reliable, thus it makes the generalized reflection‐transmission coefficients method applicable to computation of normal mode in various stratified earth models.