LAUSR

Abstract A normal-fault earthquake (Mw = 7.1) occurred in the state limit of Puebla and Morelos on September 19, 2017, exactly 32 years after the 1985 Michoacan Earthquake. A total of 5765 buildings suffered damage in Mexico City and about 300 in Puebla City. The authors carried out a reconnaissance of Mexico City, and some locations in the states of Puebla and Morelos, to identify the affected areas and the extent of damage. This report is a summary of the damage characteristics observed during the survey for both structural and geotechnical aspects. A series of microtremor measurements were taken to understand the ground motion characteristics in three key areas of the Mexico City Basin. The results are presented and compared to the data gathered from the accelerograph network available in Mexico, and the damage characteristics are discussed. Whenever relevant, the conditions before the earthquake are compared with the damage encountered by the inclusion of photographs. In order to understand the extent of the damage incurred by the 2017 earthquake, an overview is provided of the geological and geotechnical conditions of Mexico City, which is renowned for its soft soils and problems associated with those soils. Given that the 1985 Michoacan Earthquake established the standards for seismic design in Mexico City, this report provides background on the effects of the 1985 earthquake and comparisons are made with the Puebla earthquake.