Ricardo Taborda

We present a study of the ground motion and resulting amplification in the Mexico City Basin due to strong earthquakes in the Mexican Pacific Coast. We propose a refined structure of the Valley of Mexico and the Volcanic belt as well as a regional structure which includes a step in the subduction zone. Our study compares two sets of three dimensional simulations: the first includes the Valley of Mexico, while the second excludes the soft soil deposits. The 3D computations performed, with a maximum resolution of 0.75 Hz, reproduce the amplitude and long durations characteristics usually observed in the basin. Stations inside the Mexican Volcanic Belt experience amplification confirming the observation by Baker et al. (1996). In the frequency band 0.2-0.4 Hz additional amplification occurs inside the valley due to the shallow soil deposits in the lake bed region. We compare the normalized durations of the ground motion at several stations against observed data, and speculate on the durations of the soil motion as being a local effect due to the basin’s shape and low velocities.