RESONANCE THEORY OF ELASTIC HEAD WAVES PROPAGATING IN A SOLID LAYER IN TIGHT CONTACT WITH A THICK SOLID BASE

The boundary value problem of elastic wave propagation in the case of a plane solid layer I in tight contact with a thick solid base II with a monopole sonic source placed in layer I is treated analytically by the standing wave method. Solution in the form of contour integrals wi th the amplitudes in 2 x 2 matrix form are obtained. An inspection of the solution shows that it contains all well-known component waves exc ept the head waves. Particular interest is put on these latter waves. Three kinds of head waves (P, S, and S-1) are obtained. The S-1 wave i s newly predicted, which propagates with the shear wave velocity of th e soft layer I. It may be considered as the candidate for the ''late S wave'' observed in earthquakes. The resonance frequencies of the thre e head waves are obtained, and the motion of the free surface is also described for the three cases.