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An intraslab normal-faulting earthquake struck the central region of Mexico on 19 September 2017, leading to the collapse of 44 buildings in Mexico City. After the earthquake, the authors collected information in situ and through social media about the collapsed buildings, which was statistically processed to identify the causes of their collapse. This article presents the main collapse statistics, which revealed that 64% of the collapsed buildings had between 1 and 5 stories, 61% had a seismic-force-resisting system based on reinforced concrete columns with flat slabs, 57% experienced a soft-story mechanism, 91% were built before 1985, 43% were located at the corner blocks, and 10% exhibited pounding with neighboring buildings. The spatial distribution of the collapsed buildings and the recorded ground motion features suggest that short- and medium-period buildings having well-known vulnerabilities were particularly prone to collapse under amplified high-frequency seismic waves typical of intraslab normal-faulting earthquakes, such as the 2017 Puebla–Morelos earthquake.

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