Quantification of the Effects of an Urban Layer on Rayleigh Wave Characteristics and Development of a Meta-City.

This paper presents the quantification of the role of structural parameters and impedance contrast in the insulation and meta-capacity of a city for Rayleigh waves at an earthquake engineering scale. The feasibility of developing heterogeneous and homogeneous meta-cities in a soft sediment deposit is investigated using the meta-behavior of structures and meta-blocks in the epicentral zone of shallow crustal earthquakes. The Rayleigh wave and horizontally propagating plane SH-wave responses of the city with different structural parameters and impedance contrast are simulated at the top of the structure as well as at the free field after crossing the city. It is concluded that the structures act as a meta-structure for the Rayleigh waves but not for the Love waves, and the meta-capacity of the city increases with the increase in the number and stiffness of structures and decrease in damping and impedance contrast. An increase in the width of bandgaps at different longitudinal modes of vibration of structures is obtained with a decrease in impedance contrast, particularly when it is less than 15. It is concluded that meta-blocks can be developed using appropriate ceramic material considering the half-space impedance to develop a desired bandgap for Rayleigh waves. Based on the obtained increase in the city's insulation capacity for Rayleigh waves with the increase in the number and width of structures and decrease in impedance contrast, it is recommended that engineers consider the urban layer as lying in the path of Rayleigh waves for the estimation of seismic hazard in the epicentral zone of shallow crustal earthquakes. [ABSTRACT FROM AUTHOR]