Fig. 4: Rayleigh waves in bound media.

a Calculated eigenfrequencies \(\widetilde{\omega }\) (dots) of a finite slab with periodic boundary conditions in the horizontal directions compared to the theoretical solution (solid line) of a half-space. Inset: one representative Bloch wavefield at the selected point. b Eigenfrequencies of individual letters (numerically calculated), i.e., "UC3M" as depicted below. c Simulated displacement fields when the letters are excited by local vibrations (red stars, ω = 15π). In the calculation, the parameters are specified as α = 1, μ = 0.5, A = 0, and K^o = 0.5, and the wavefields are normalized with regard to their own maximum values.