Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

This study presents a methodology developed to evaluate the contribution of the characteristic frequency of each layer to the fundamental period of vibration from the inversion of apparent dispersion curves obtained from a surface-wave survey using an active source, independent of the velocity of each layer. The calculation of the fundamental period was achieved using the simplified procedure developed by Dobry et al. (1976) for a linear soil profile. For the classification of shear-wave velocities, a modification of the International Building Code (IBC, 2009) was used for the subsoil material in the city of Querétaro. The main geological units were grouped into three stratigraphic sequences: the plateau volcanic rocks that constitutes the high topographic elevations that surround the valley, the slope deposits composed of volcanic and sedimentary deposits (alluvial), and the plain sequence comprised of stratified deposits of lacustrine, fluvial and volcanic materials. From the analysis of the shear-wave velocity profiles, we observed layers with low shear velocities confined within high shear-velocity strata, indicating the presence of low stiffness layers at different depths. For the rock sequences, the fundamental period of vibration is short (less than 0.1 s), while this period is longer (greater than 0.3 s) in the plain deposits. In the slope area, the period is relatively long (variable from 0.1 s to 0.3 s) possibly due to a topographic effect. The results obtained in this study show that the methodology proposed to evaluate the dominant period from the integration of the characteristic frequencies obtained with surface waves, allows us to estimate the thicknesses and shear velocities of each layer, the fundamental period of each stratigraphic sequence and finally, their site spectra.

A comparison of the seismic response and environmental impact potential of two building systems is presented. Both buildings have 24 floors and a total height of 114 meters, and are in the Lake Zone of Mexico City. The first building, denominated traditional, uses composite (steel and reinforced concrete) moment-resisting frames and concentric diagonals. The second one, denominated innovative, is structured with steel perimetral diagonal grids and steel frames. Despite its lower weight, and smaller lateral strength and stiffness, the innovative system exhibits a superior seismic performance characterized by light damage on approximately 8% of its seismic-resistant elements for the design seismic excitation. Also, the construction of the innovative system reduces in two thirds the emissions of greenhouse effect gases with respect to its traditional counterpart. The example presented herein provides an idea of the benefits that the use of innovative systems can bring to the Mexican design and building practices.