SEISMIC METAMATERIAL FOR SURFACE WAVE

Abstract

Background: In this report chapter 2 presents Simulation of Rayleigh Wave Generation in homogeneous Medium using Finite Difference Method at the critical distance with and without free surface response and the amount of SV wave energy converted into Rayleigh wave. In this chapter, numerical quantification of variation of dominant frequency and spectral amplitudes of the generated Rayleigh waves at the critical distance with focal depth and the parameters of source time functions used to incorporate point earthquake source in the numerical grid (critical distance is the distance from the epicenter at which direct incident SV-wave causes evanescence P-wave with the angle of reflection as 900). It is concluded that the coupling of evanescence P wave caused by the incident SV-wave at the critical distance with the reflected SV-wave generates Rayleigh waves. In this report chapter 3 presents whether a water body falling path of Rayleigh wave can act as metamaterial for seismic wave or not and whether Rayleigh wave can propagate in a water body. If yes, what will be the terms and conditions. Further, whether the deep-water body in front of a fort was seismically beneficial to it or not in the case of Rayleigh waves caused by very shallow earthquake. To fulfil the aim and to find out the question raised, we have simulated the Rayleigh wave responses of a small water body as well as the river for different width and depth and analyzed. The analysis of Rayleigh wave responses of the small water body as well as the River models reveals that Rayleigh wave can propagate through water. The water body is not acting as meta-material.In this report chapter 4 present boreholes filled with air or soil can act as a sub-wavelength resonator, which in turn may develop a bandgap in a frequency band of earthquake engineering. A very good match of bandwidth of the SRDs with the fundamental longitudinal mode of vibration of the borehole filled with sediment reveals that BHSD models can be used to protect the specific type of buildings from the Rayleigh waves in the epicentral zone of shallow crustal earthquake. Further, the value of SRDs and associated bandwidth is highly affected by the CC-distances.