A special eigenmode to induce bandgap and attenuate low-frequency seismic surface waves

Controlling low-frequency surface waves by subwavelength seismic metamaterials has gained wide attention in engineering and science. By comparing the mode deformation distribution of the surface wave bandgap and passband, this study proposes a collectivization eigenmode that could induce a novel low-frequency surface wave bandgap while maintaining extreme subwavelength. We analytically demonstrate the attenuation mechanism of the collectivization eigenmode, which is compared with the traditional surface wave bandgaps, and design a subwavelength seismic metamaterial using regular building materials with a height 0.525 m. Through eigenmode analysis, we confirm the existence of the collectivization eigenmode within the designed seismic metamaterials. Furthermore, we prove that the designed seismic metamaterials generate a low-frequency surface wave bandgap in dispersion curves. Parameter analysis reveals the significant role of resonators in determining the bandgap frequency and width. To verify the surface wave attenuation, we conduct both frequency domain and time domain analyses. Results from the frequency domain shows that there is a significant attenuation at the bandgap frequency, which agrees with the dispersion curves. Finally, we conduct an in situ full-scale experiment and test the dynamic response of the seismic metamaterial to validate the effectiveness of our study. In addition, the designed seismic metamaterials show promise for controlling noise and elastic waves.