1985 Mexico City earthquake earthquakes of magnitude 7.8 or stronger in the 20th century prior to the 1985 event. However, this particular section of the subduction zone had not had an event for a much longer time. Shockwaves from the earthquake hit the mouth of the Río Balsas on the coast at 7:17 am and hit Mexico City, 350 km (217 mi) away, two minutes later at 7:19 am. The 19 September quake was a multiple event with two epicenters and the second movement occurring 26 seconds after the first. Because of multiple breaks in the fault line, the event was of long duration.
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