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A pesar de la evidencia experimental y teórica de la importancia de la topografía en la respuesta sísmica, sus efectos son poco considerados en la ingeniería práctica. En la actualidad los pocos códigos que tienen propuestas al respecto desconocen el efecto que sobre la magnitud de la variación sísmica por efecto de la topografía tienen la frecuencia del movimiento y la relación entre la longitud de onda de la excitación y el tamaño del accidente topográfico. En este trabajo, a partir de conceptos de difracción de una cuña infinita, se propone una expresión bi-paramétrica para cuantificar la variación en la respuesta sísmica en puntos localizados en la vecindad de un accidente topográfico. La expresión es derivada a partir de un análisis paramétrico en el dominio de la frecuencia sobre geometrías en forma de montaña y cañón. Las expresiones propuestas son aplicadas sobre dos casos realistas para obtener espectros de respuesta. Para medir la calidad de la propuesta, los resultados son contrastados con los obtenidos con una modelación computacional., Despite the relevance of topographic effects in seismic response by experimental and theoretical studies, these parameters is not widely used in practice engineering. Nowadays, just a few codes consider these effects, but they do not take into account the frequency of the movement and the relation between the dimensions of the topographic accident and wavelength of the incident field. A two-parameter expression for the quantification of topographic effects in ground response analysis at sites located in the vicinity of a topographic feature is presented. The expression is derived from parametric analysis of convex and concave canonical shapes after identifying that the diffracted field in these geometries remains relatively stable in the low dimensionless frequency regime. The proposed expression is used in the estimation of topographic effects at two sites located in realistic topographic scenarios over a given period range. To show the quality of the approximate formula results are compared with numerical simulation values.

Despite the irrefutable amount of theoretical and field evidence of the impact of topographic effects on the local response at a site the engineering community still lacks practical methods for its consideration in a standard routinely basis. The incorporation of topographic effects into site response analysis has been a major challenge to engineers as it involves coupling between mechanical and geometric modifications to the incident seismic waves, which at the same time demands for field data that is rarely available to the practicing engineer. On the other hand, it has been observed that the main signature of topographic effects, besides the expected change in frequency con tent, is its spatial variation. These complexities combined to the field data required to build fully coupled mechanical-geometrical models have resulted in complete under consideration of these effects. In this work we follow a rational approach to study the effect of surface topography on the response at local sites after formulating the problem following a diffraction perspective. Since this work is framed in an engineering context our main result is a method to incorporate the effect of surface topography in ground response analysis. Although the method requires numerical simulations we show that if the analyst brings into the problem the dynamic properties of the structure for which the analysis is conducted in the first place very moderate models may be required. These idea leads to the concept of size conditioned response spectra which uses a target structural response spectra to fix the size of the computational model. The resulting numerical domain turns out to be of manageable size thus it can be handled with standard computing resources. Although our proposed approach is limited to surface topography the combination of the theory of diffracted waves and the consideration of the structural response creates new venues to advance in understanding the problem of topographic effects.