Low-frequency and wide bandgap seismic metamaterials for Rayleigh wave attenuation

This study introducesa seismic metamaterial (SM) for mitigating low-frequency seismic Rayleigh waves when embedded in the ground. Dispersion curves and vibration modes of a unit cell incorporatingthe SM were calculated using the Bloch theorem and sound cone method in a numerical model. The lowest frequency of the bandgaps (BGs) is 1.6 Hz, with the maximum absolute bandwidth reaching 18 Hz, matching the seismic wave considered in this study. Furthermore, a comprehensive analysis of vibrational modes revealed the mechanism responsible for BG formation. Numerical simulations in both the time and frequency domains confirmed the attenuation of Rayleigh waves by finite models containing SMs, along with theconversion of Rayleigh waves into body waves. Additionally, the effects of material and geometric parameters on BG frequency range is discussed. Complex SM structures were devised by combining two distinct SMs with varying geometric parameters, achieving a complete broadband attenuation range. Finally, realistic seismic Rayleigh wave propagation through complex SMs was simulated, conclusively validating their effectiveness in providing broadband attenuation.