Resonant metabarriers as seismic attenuators in granular media

Arrays of surface resonators forming so-called metabarriers are capable of converting seismic Rayleigh waves into less dangerous shear waves traveling in the bulk, attenuating the ground motion at the surface. However, this phenomenon pertains to resonant materials inserted in homogeneous media which feature properties rather different to those of natural soils. In this work, we experimentally investigate the ability of a resonant metabarrier embedded below the surface of an inhomogenous medium, i.e. a granular unconsolidated material, to attenuate the incoming surface waves. Although unable to diverge their propagation into the bulk, we find that surface resonators in granular media achieve attenuation of Rayleigh waves by up to 50 % around their resonant frequency. The findings can be used as a starting point for future real-scale implementations for seismic protection systems in stratified soils presenting an inhomogeneous stiffness profile at the seismic Rayleigh waves scale.