The 1985 Mexico City earthquake of September 19 , 1985 is a good example of earthquake damage to a modern city built on soft sediment . Though the earthquake epicenter was located around 350 km from the city , the sites with soft clay deposits exhibited a huge amplification of ground motion resulting in severe damage . Mexico City is built on a thick layer of soft soil over a hard stratum . The western part of the city is located on the edge of an old lakebed , whereas , soft clay deposits filling the former lakebed underline the eastern part . In the lake bed area , the soft clay deposits have shear wave velocities ranging from 40 to 90 m/s and the underlying hard strata has a shear wave velocity in the range 500 m/s or greater . During the earthquake of 1985 , the seismic waves were trapped in the soft strata . The soft soil layer allowed the upward propagating shear waves to propagate easily ; however , the hard strata at the bottom acted like a reflector and bounced back the downward propagating waves . This kind of trapping of waves created a resonance and consequently resulted in an enormous amplification of the ground motion . As a result , the lake bed area suffered catastrophic damage ; however , in the southwest part of the city , ground motions were moderate and building damage was minor . The acceleration recorded in the hill-zones were relatively low-amplitude , short period ground motions compared to high amplitude and long period ground motions recorded at stations located in the lake zone
1985 Mexico City earthquake
1985 Mexico City earthquake
Seismic microzonation