Seismic Amplification of Peak Ground Acceleration, Velocity, and Displacement by Two-Dimensional Hills

There are valuable investigations on the amplification effects of the topography on the seismic response in the frequency domain; however, a question is that how one can estimate the amplification of time domain peak ground acceleration (PGA), peak ground velocity (PGV), and peak ground displacement (PGD) over the topographic structures. In this study, the numerical approach has been used for the evaluation of time domain peak ground motion parameters amplification on a two-dimensional Gaussian-shaped hill in a typical rocky medium. Five normalized geometries, as well as the twelve normalized vertical incident motions, have been used. Incident motions are SV wave of Ricker type. Time domain responses of displacements, velocities, and accelerations have been calculated and analyzed in selected points of the hills. Tabulated results illustrate a significant role of geometry on the patterns of the amplification, and that almost the top of the hill amplifies and the hill toe de-amplifies the motion. Meanwhile, the rate of the amplification and de-amplification generally depends on the predominant period of the incident motion. Comparison of the amplification of PGA, PGV, and PGD values with the Fourier amplification curves showed that, in general, there is a well-matched correlation between them; however, the time domain amplifications of PGA, PGV, and PGD values have a gentler variation with the predominant period of the motion. It seems that one can give a reliable estimation of time domain amplification of PGA, PGV, and PGD values by using averaged Fourier amplifications over the suitable range of frequencies around the predominant period of the input motion.