Ground motion variability in the virgin Texcoco Lake area, Mexico

Luis Osorio, Juan M. Mayoral

In the proceedings of: GEO2011: 64th Canadian Geotechnical Conference, 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, 5th Pan-American Conference on Teaching and Learning of Geotechnical Engineering

Session: Earthquake Engineering & Geophysics

ABSTRACT: Spatial ground motion variability observed in the Texcoco lake region, in the surroundings of Mexico City, has been studied through the generation of sets of site specific response spectra developed performing several 1-D stochastic site response analyses. The studied zone has an area of 19.0 by 5.5 km2, and has been instrumented with four seismological stations, which have recorded strong ground motions over the past years. This area presents unique geotechnical subsoil conditions consisting on very soft clays deposits, with low shear strength and high compressibility, randomly interbedded by sand lenses. The subsurface conditions prevailing at the instrumented sites, including shear wave velocity distribution with depth, were characterized using standard penetration, SPT, and cone penetrations, CPT, tests, combined with selective sampling of undisturbed soil specimens. Uncertainties associated with shear wave velocity measurements were considered allowing a random variation of +/-30% around the mean values. Series of resonant column and cyclic triaxial tests were carried out to obtain the dynamic soil properties. From this work, response spectra for the studied area were proposed. These can be used in future updates to the Mexico City building code.

RESUMEN: En el pasado, en estudios realizados de análisis de respuesta de sitio estocásticos unidimensionales, se han observado variaciones espaciales de los movimientos de suelo en la región del ex Lago de Texcoco. Para evaluar este fenómeno en este trabajo se consideró una zona de estudio de 104.5 km2, que se instrumentó con cuatro estaciones sismológicas, que cuentan con registros de sismos fuertes. Esta región presenta condiciones geotécnicas difíciles debido a la presencia de depósitos de arcillas blandas lacustres altamente compresibles, de espesores importantes, intercalados aleatoriamente con lentes de arenas y limos. De esta zona se tiene información de la distribución de la velocidad de onda de cortante con la profundidad, obtenida a partir de la caracterización con pruebas de penetración estándar, SPT, y penetración de cono, CPT, combinado con muestreo de suelo inalterado y alterado. Las incertidumbres asociadas con la velocidad de onda de cortante se tomó en cuenta variando aleatoriamente el valor de la velocidad media +/-30%. Además se realizaron series de pruebas de columna resonante y triaxial cíclica para obtener las propiedades dinámicas de los suelos. De este trabajo se obtuvieron los espectros de respuesta para el área de estudio, que en el futuro podrían ser incorporadas en el código de construcción de la ciudad de México.

Access this article:
Canadian Geotechnical Society members can access to this article, along with all other Canadian Geotechnical Conference proceedings, in the Member Area. Conference proceedings are also available in many libraries.

Cite this article:
Luis Osorio; Juan M. Mayoral (2011) Ground motion variability in the virgin Texcoco Lake area, Mexico in GEO2011. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GEO11Paper217,author = Luis Osorio; Juan M. Mayoral ,title = Ground motion variability in the virgin Texcoco Lake area, Mexico,year = 2011}