Solid–liquid interface: Appearing induced supersonic head waves in liquid layers

The current research is concerned with the analysis of the reflected-refracted bulk waves at the interface between elastic isotropic substrate and a liquid overlaying layer. It is shown that at a certain angle of incidence, the S wave in a substrate generates a “geometric” SP head wave, which leads to the appearance of an induced head wave in the liquid layer. This induced head wave may propagate in the liquid layer at a supersonic velocity exceeding the bulk wave velocity in the liquid. The analysis is based on the Helmholtz decomposition of the displacement field, along with the decompositions of stress and strain tensors into spherical and deviatoric parts. It is anticipated that the possible appearance of induced supersonic head waves in the liquid layer can find applications in theoretical and applied geophysics.