A new iterative method for finding the normal modes of a laterally heterogeneous body

We present a new iterative method for finding the normal modes of a laterally heterogeneous body. The number of operations used by our method is proportional to the square of the number of basis functions used, while the effort required by the variational method increases as the cube of the number of basis functions. A numerical example shows that, at least for lower order modes, our iterative method yields results which are as accurate as the variational method.