Abstract

The September 19th, 2017 M7.1 Puebla-Mexico City earthquake introduced strong ground motions into the Mexico City basin, which contains very soft lacustrine soils, dense urban infrastructure, and millions of inhabitants. As a result, 38 mid-rise structures collapsed and several hundred more were damaged. This paper reports the observations related to building performance, damage patterns, and foundation performance made by the two UNAM-GEER engineering reconnaissance teams sent to investigate the geotechnical aspects of the earthquake. The methodology used to perform building damage mapping following the 2017 event is described. Comparisons are made between the observed building damage patterns following the September 19th, 1985 and the 2017 earthquake, and the distinct differences in the damage pattern distribution between the two earthquakes are summarized. Overall, building and foundation performance were observed to be quite good during the 2017 event, especially when compared to the 1985 event. Structures that were observed to be heavily damaged or collapsed were all built prior to 1985, and incorporated poor structural design and/or construction which resonated with the soil column on which they were constructed, and/or were built upon very soft soils that contributed to significant foundation deformations. Detailed building damage pattern maps of specific neighborhoods that were investigated are provided, and lessons learned from this event are summarized.