1985 Mexico City earthquake the city. However, none of these regulations had an event like 1985's in mind when passed. Most of the seriously damaged buildings were built between 1957 and 1976, when the city was starting to build upwards, in the six-to-fifteen floor range. In second place were buildings from before 1957, possibly because they were weakened by the earlier earthquakes. Structures built between 1976 and 1985 suffered the least damage. At the time of the earthquake, Mexico City had one of the most stringent building codes, based on experience gained from earthquakes in 1957 and 1979. However, the codes were not designed
1985 Mexico City earthquake their own frequencies of vibration. Those that are six to fifteen stories tall also vibrate at the 2.5-second cycle, making them act like tuning forks in the event of an earthquake. The low-frequency waves of an earthquake are amplified by the mud of the lakebed, which in turn, is amplified by the building itself. This causes these buildings to shake more violently than the earthquake proper as the earthquake progresses. Many of the older colonial buildings have survived hundreds of years on the lakebed simply because they are not tall enough to be affected by the resonance effect. The earthquake