1985 Mexico City earthquake 1985 Mexico City earthquake The 1985 Mexico City earthquake struck in the early morning of 19 September at 07:17:50 (CST) with a moment magnitude of 8.0 and a Mercalli intensity of IX ("Violent"). The event caused serious damage to the Greater Mexico City area and the deaths of at least 5,000 people. The sequence of events included a foreshock of magnitude 5.2 that occurred the prior May, the main shock on 19 September, and two large aftershocks. The first of these occurred on 20 September with a magnitude of 7.5 and the second occurred seven months later on 30 April
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