The Mexico Earthquake of September 19, 1985—Seismic Zoning of Mexico City after the 1985 Earthquake

Using a simplified method for the evaluation of the seismic capacity of medium rise concrete structures, it was possible to obtain the base shear coefficient corresponding to failure (resistance coefficient) for 162 buildings, and use it as an evaluation index. The resistance coefficients of the 90 evaluated structures that suffered severe damage were used to elaborate a map of intensities for the 1985 Mexico City earthquake. This map shows the strong interaction of neighboring zones of firm soil or rock that amplify the ground motion in the soft soil between them as much as 100%, this being the main reason for the high intensities observed in some districts of the city. Based on these results, a new seismic zoning was proposed for the chapter of the 1987 Mexico City Building Code.