The September 19, 2017 Mw 7.1 Puebla-Mexico city earthquake: Important findings from the field - Overview of Special Edition

The September 19th, 2017 Mw 7.1 Puebla-Mexico City earthquake lead to strong ground shaking in the densely populated Mexico City basin, and surrounding country areas in central Mexico. As a result, 38 mid-rise buildings collapsed and several hundred more were damaged in Mexico City, and extensive damage was observed in the states of Puebla and Morelos. This special edition synthesizes observations related to structural and foundation performance, and the corresponding damage patterns, carried out by two UNAM-GEER engineering reconnaissance teams sent to investigate the geotechnical earthquake engineering aspects of this event. Articles were solicited of researchers that were in the field that investigated: the characteristics of the event, the demand and damage distribution across Mexico City and surrounding regions, the seismic performance of buildings, lifelines, and other critical infrastructure, considering the site response and soil-structure interaction effects in the observed damage distribution. Special attention was paid to the impact of regional ground subsidence, in the seismic-soil structure interaction exhibited by the affected building. Advanced non-intrusive survey methods were used to map damage patterns in a regional level. Comparisons were made between the observed building damage patterns following the September 19th, 1985 Michoacan earthquake, and the 2017 Puebla-Mexico City earthquake, and the distinct differences in the damage distribution between the two earthquakes were revised. 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 in each research paper include in this special issue.