Severe seismic effects and regional ground subsidence are well recognized conditions that should be considered for the design of foundations in Mexico City. These phenomena are magnified by lacustrine clayey soft deposits with very high compressibility and very low shear strength, which are found at the extensive Lake Zone of the city. To clarify the soil-structure interaction phenomena, a prototype foundation was instrumented, selecting a friction-piled support of an urban bridge located in the Metropolitan area of Mexico City. Soil-raft contact pressures, loads on selected piles, and pore water pressures in the subsoil below the foundation have been monitored continuously, since the beginning of the foundation construction eight years ago. The long-term performance of the foundation is known in terms of these state variables. The response of the soil-foundation system has been recorded during the occurrence of ten mild to strong earthquakes. Time-records of those geotechnical variables were obtained at the very moment of the earthquakes, additionally to the accelerograms. This case history yielded valuable information about the foundation performance before, during and after seismic events, regarding the analysis, design and regulations for this kind of foundation
