Modelling and Clarification of Leaky Surface Wave

It is first clarified that complex roots do not really exist in elastic media. Extraneous roots are resulted from rationalization of the dispersion equation. These extraneous roots are complex when the Poisson’s ratio is high and their real parts do not really correspond to the spectral peak of Green’s functions. Leaky modes (i.e., local energy peaks in the dispersion image arise at locations where roots of dispersion equation do not exist) can be clearly identified by the local minima of det(K), while the dispersion equation is det(K)=0. Therefore, by finding the local minima of det(K), one can find all normal modes as well as the leaky modes. In this regard, leaky modes can be simply treated as higher modes. The surface leaky mode is intrinsic in vertically-loaded surface waves (i.e., Rayleigh waves). It exits even in homogenous half-space and is more pronounced in the radial component and when surface Poisson’s ratio is high. Further study examines other types of leaky mode in layered media and their implications to seismic testing will be discussed.