Why was building damage so extensive in the 1985 Mexico City quake?
1) Much of the city was built on lake silts and former swampland that vibrated with the same 2 second period as, and amplified the incoming surface waves
2) the steel frame buildings were rigid and lacked the flexibility to withstand lateral swaying during even a moderate magnitude quake
3) the richter magnitude was 8.8 and the focus was only 25 km away
4) the epicentre was right in the city