On 19th September 1985 a powerful earthquake affected Mexico City.
The earthquake itself occurred in the Pacific, some 217 miles from the city, and was a magnitude 8.1 event. There had been a smaller, 5.2 magnitude quake, back in May of the same year. The main quake on 19th September was followed by two aftershocks; one the next day and the other seven months later, which were 7.5 and 7.0 respectively.
The exact number of deaths caused by the quake is uncertain; it ranges from an estimated 10,000 all the way up to 40,000. The energy release was an estimated 21 megatons; Little Boy, which was dropped on Hiroshima, was 16 kilotons.
Image: By United States Geological Survey [Public domain], via Wikimedia Commons (en.wikipedia.org/wiki/File:1985_Mexico_Earthquake_-_Collapsed_General_Hospital.jpg)