On Sept. 8, a magnitude 8.1 earthquake struck off the southern coast of Mexico. At least 61 people died from the quake, with many more injured. Hundreds of buildings were rendered uninhabitable, with billions of dollars of property damage throughout the area. While it was the most destructive in nearly a century, the quake was less destructive than what was to come.
Less than two weeks later, just hours after the anniversary of the 1985 quake, a less powerful magnitude 7.1 earthquake struck much closer to Mexico City. Due to the latter striking closer to the heart of the capital, at least 355 casualties were sustained, many more than the Sept. 8 disaster.
Unfortunately for the millions of people inhabiting the area in and surrounding the Mexico City metropolis, any earthquake caused by the slippage of any nearby fault lines is amplified considerably.
Like many cities across the world, the Mexican capital is built in a risk-prone area. In this case, the city is built on the ancient lakebed of Texcoco, the body of water surrounding the infamous Aztec city of Tenochtitlan. Over a period of centuries after the Spanish conquered and razed the ancient city, the Spanish began draining the lake in order to lay the groundwork for the modern city.
The Spanish filled in the lake with soft materials, such as clay, from the lakebed. These materials, when hit with an earthquake, cause oncoming energy waves to slow down, making the earthquake increase in magnitude and settle for longer than it would if the ground were firm. This, combined with the nearby tectonic plates rubbing against one another, creates a “perfect storm” for earthquakes, and explains why the Mexico City area is both susceptible to repeated quakes and the damage caused is much greater than it otherwise would’ve been.
However, this isn’t the only city built on shaky ground. After the 1906 earthquake in San Francisco, a policy of quick reconstruction was pursued. Since the state and city as a whole didn’t want to scare off investment , city officials and businessmen worked together in order to get the city back up and on its feet at lightning speed.
To facilitate this, entire buildings and remnants of others were pushed into the bay where the land touched the ocean. Since what few regulations on safety at the time were quickly discarded to create a “clean slate” for the new San Francisco, much of the modern day city is essentially built on trash. While today this policy would never have even been considered, in the period immediately following the quake it made good business sense. Citizens were amazed as plumbing was up and running again within days, and entire buildings were erected in just weeks.
However, as many geologists are warning today, San Francisco could suffer a fate similar to Mexico City. Much of what is now the city’s downtown is in fact built over the rubbish of the old city. While many of the larger buildings are cemented in the much safer bedrock, other older, less stable ones are not as fortunate. As a result, when the next “big one” strikes, which is long overdue , many buildings will simply collapse due to a process known as liquefaction (a process in which soil loses strength due to an earthquake, making it perform as a liquid would).
As more and more people move into cities, some of which are constructed near fault-lines, it’s important for government officials to take the necessary precautions in ensuring that when and if a substantial quake hits, such as the one in Mexico City, unnecessary loss of life is avoided. If such planning isn’t taken into consideration when constructing or expanding many of the world’s cities, stories such as this one may hit much closer to home with increasing frequency.
Jesse Shoghi is a junior studying computing.