Acceleration-time history; Cone penetration; Cyclic triaxial tests; Design earthquakes; Dynamic property; Earthquake ground motions; Earthquake recording; Empirical correlations; Geotechnical; Geotechnical conditions; Ground motions; Ground response; In-situ measurement; Laboratory investigations; Lacustrine clay; Lake areas; Me-xico; Probabilistic analysis; PS-logging; Random variation; Random vibrations; Resistance values; Resonant column; Response spectra; Seismic; Seismic station; Shear wave velocity; Site response; Spatial variations; Spectral matchings; Standard deviation; Strain levels; Thick deposit; Time domain; Acoustic wave velocity; Clay deposits; Dynamic response; Geotechnical engineering; Lakes; Shear waves; Soil mechanics; Soils; Time domain analysis; Earthquakes
Texcoco lake area, in the valley of Mexico, presents particularly difficult geotechnical conditions due to the presence of thick deposits of soft, highly compressible lacustrine clay, randomly interbedded with sand lenses. In contrast to other sites in the valley, there is a lack of information regarding geotechnical subsoil conditions, dynamic properties, and earthquake recordings at rock sites. Thus, the seismic environment is not completely identified. This paper describes field and laboratory investigation as well as analytical studies, aimed at characterizing the ground response this region. In-situ measurements of shear wave velocity, using suspension PS logging, along with cone penetration, CPT, and standard penetration, SPT, resistance values, and results from series of resonant column and cyclic triaxial tests were used to obtain a representation of the subsoil characteristics found at the site, and the variation of dynamic properties with strain level. Predicted shear wave velocity profiles derived from empirical correlations compare well with measured values. Ground motion definition was achieved indirectly through empirically derived response spectra obtained from sets of earthquake ground motions recorded by four seismic stations located in the area. Acceleration time histories representative of the design earthquake were obtained using time-domain spectral matching. 1-D shear wave deconvolution was used to obtain the corresponding ground motions in rock. With this information, probabilistic analyses of site response were carried out at several points. The response of the system was obtained in terms of power spectrum using the random vibrations theory. In order to consider the potential variability in the subsoil dynamic properties, a random variation of the shear wave velocity was also accounted for in this study, taking the mean and plus one standard deviation values. Finally, a set of response spectra that defines the spatial variation of dynamic response the studied area was obtained. © 2009 IOS Press.