Considerations on seismic microzonation in areas with two-dimensional hills

This paper presents the results of an extensive numerical parametric study on seismic behavior of 2D homogenous hills subjected to vertically propagating incident SV waves. It is shown that the amplification potential of these hills is strongly influenced by the wavelength by the shape ratio, by them shape of the hill and in a less order of importance, by the Poisson ratio of the media. The 2D topography effect could be ignored, only if the hill has a shape ratio of less than 0.1 or if it is subjected to incident waves with predominant dimensionless periods of greater than 13 times the shape ratio. In incidence of waves with wavelengths longer than the width of the hill. the amplification curve usually finds its maximum at the crest and decreases towards the base of the hill. Else!, some de-amplification zones would occur along the hill. Among hills with similar shape ratios, those with intermediate cross section areas show intermediate seismic behavior, too. Estimated seismic site coefficients for the crest of a 2D rocky hill depend on its shape ratio and could reach even 1.7. which encourages one to classify it according to standard site categorization procedures as soil profile types SC or SD instead of the conventional SB type.