Mexico City is NOT particularly vulnerable because it was build on TOP of Tenochtitlan. MC is vulnerable because it an Tenochtitlan were built on top of a lake bed.
I was in the July 28, 1957 quake which was 7 or 7.5?? I was walking home from a party with a friend about 1:30am. I started to stagger and said, “But I only had 2 drinks.” My friend from San Jose, CA, cried,”It’s an earthquake,” grabbed my hand and we ran to the intersection and stood in the middle of the street. Along the sidewalk were 3 story buildings, the telephone poles were swaying back and forth, the wires were slapping against each other, but otherwise it was very quiet. We held each other from falling and swayed and rotated from side to side like standing in a fast moving NYC subway train. It lasted over a minute. He walked me home and when I arrived all the 3’ high planters had fallen over in the hall. The maid was hiding in the dirty linen under the dining room table, the guy upstairs had been thrown out of bed, and one of the girls in the front room of my apartment had fled the room as it looked like a palm tree was going to fall into the 3rd floor window. She saw the living room chandelier swing hitting the ceiling on one side and then hitting the ceiling on the other side. The next day I walked all over taking photos. I still have them. The 20? story Goodyear? office building had broken windows and cracks running all over the surface. A friend who was downtown said the modern “little Empire State Bldg.” was swaying back and forth, and the whores were running out into the street screaming and praying. For days afterward especially if I was lying down I could feel aftershocks. The first link is three pages of news reports. The second link is a technical report. The third link is images, but most are from 1985 or this year. The damage shown is mostly too severe for 1957.
http://archives.chicagotribune.com/1957/07/29/page/1/article/quake-in-maxico-kills-42
http://www.iitk.ac.in/nicee/wcee/article/vol.1_session5_359.pdf