Amplification of linear strain in a layer excited by a shear-wave earthquake pulse

摘要

Peaks of transient strains in a layer over semiinfinite half space are amplified byinterference duringudup- and down-propagating waves, and they depend upon the impedance ratio of the layer and of theudhalf space, as well as the wavelength.The amplification of incident motion on the ground surface isudusually described in the frequency space for the response to a steady state, periodic excitation. Toudunderstand how this amplification develops for transient responses and for applications in which theudlinear theory leads to satisfactory answers, this paper describes the amplification in time in a layerudexcited by a shear wavepulse. It is shown that the maximum amplification is equal to 2 for a ‘‘stiff’’ layer on a ‘‘soft’’ halfspace, and equal to 4 for a ‘‘soft’’ layer on a ‘‘stiff’’ halfspace, when the layerudthickness corresponds to the quarter wavelength of the wave in the layer.