Yesterday, Mexico City was struck by a powerful 7.1-magnitude earthquake. As of today, over 200 people have been reported dead as rescuers continue their efforts to recover those still trapped in the rubble. Dozens of buildings in and around the city were reduced to rubble and many more, severely damaged. Mayor Miguel Angel Mancera said buildings fell at 44 places in the capital alone, including a primary school where 25 bodies have since been recovered. 

The temblor is the deadliest the country's capital has seen since a 1985 earthquake on the same date, exactly 32 years prior, killed thousands. Mexico sits at the boundary of three fault lines—a very active seismic zone that makes the area extremely vulnerable to earthquakes of high magnitude that are capable of destroying whole buildings and ripping façades off others. Just 12 days before, the country endured its second-largest earthquake in history when an 8.1-magnitude shake hit the states of Oaxaca and Chiapas. 

Mexico City, itself, is exceptionally vulnerable to damage due to the fact that it is largely built on a dried lakebed. According to the National Oceanic and Atmospheric Administration, "these soft sedimentary clay deposits amplified the seismic waves, or they liquefied, destroying the foundation of some buildings" during the 1985 quake. A result of being built on a sinking lake bed, the city and its buildings were once again made vulnerable to collapse yesterday. 

The 1985 earthquake flattened 30,000 buildings and damaged 68,000 more. A year later, new laws came into place that required builders and architects to account for loose soil and required authorities to fully inspect and supervise building processes. Since then, large swaths of the city have been rebuilt as millions of dollars have poured into making the capital a major tourist destination; however, the recent devastation calls into question the success of these measures and whether or not new regulations were always followed.

While many past vulnerabilities have been minimized, plenty of the buildings in the capital are pre-1985 and while policies of regularization on existing structures were implemented, they were often incomplete and not lasting. As far as new construction goes, new updates to building codes have not necessarily corresponded to an increase in the construction knowledge of local practitioners, meaning that construction codes are often not followed due to misunderstandings and an inability to correctly apply regulations. 

... people in Mexico, as in much of Latin America, tend to build their own homes or do their own renovations, knocking walls through or installing windows and changing the specifications so that they might no longer fit the code to which they were built

Moreover, many of the improvements and efforts to make the area more resilient have been concentrated to the city's central areas. On the periphery, informal settlements have continued to crop up in the subsequent decades due to the rising cost of living in the city center. According to a UN Report, irregular settlements—around 900 in greater Mexico City—occupy approximately half of the urban area and are home to sixty percent of the metropolitan population. Here, building codes rarely impact construction methods and do not follow housing regulation. 

Engineering lecturer Christian Malaga-Chuquitaype, from Imperial College London, told the BBC that "people in Mexico, as in much of Latin America, tend to build their own homes or do their own renovations, knocking walls through or installing windows and changing the specifications so that they might no longer fit the code to which they were built."

The Mexico City government maintains a "zero-tolerance" policy with respect to informal settlements, meaning that neither state infrastructure nor state services flow there. While meant to discourage settling on the periphery, it has done little to prevent the economic and social inequity forcing migrants to settle on the urban outskirts. It has also ensured that vulnerability-reducing regulations are not reaching large classes of housing and that the very population most vulnerable in earthquakes are being denied crucial resources.