What is land subsidence?
It is possible that Mexico City (CDMX) will soon cease to be the same as we know it due to a decrease in the soil’s resistance capacity. Land subsidence is currently affecting most of the infrastructure of the world’s largest city to the point of putting the population at risk.
This paper reports the findings of a documentary research that analyzes, synthesizes and describes with a qualitative approach the risk of the population living in Mexico City due to cracks and sinkholes generated by ground subsidence.
For its study and identification, two categories or types have been proposed in Mexico: the first, known as Mexico City Type Subsidence (STCM), is characterized by the formation of a concentric circular pattern at regional level caused by the consolidation of the existing material (highly compressible clays); the second is Structurally Controlled Differential Subsidence (SDCE), in which the zone of greater affectation is close and aligned with the direction of a controlling tectonic structure (for example, a pre-existing geological fault).
My house is sinking
By 2040, 19% of the world’s population – representing 21% of global GDP – will be affected by the sinking of the ground surface; a phenomenon often caused by human activities, such as groundwater extraction.
To generate this data, Gerardo Herrera García and the other experts made a global map of land subsidence caused by groundwater extraction from subway aquifers. They then developed a model combining spatial and statistical analyses that identify the susceptibility to subsidence of an area, depending on factors such as flooding and groundwater depletion caused by human activities.
The team was soon joined by other researchers, such as Marta Béjar Pizarro, Juan López Vinielles and Rosa Mateos, from the IGME; Roberto Tomás, from the University of Alicante; and scientists from UNESCO’s International Subsidence Initiative.
“We achieved a model that explains where this phenomenon can occur,” says García Herrera. That is, they managed to make a world map in which the areas susceptible to subsidence are marked.
How to solve the sinking of a house
Currently, a group of researchers from UNAM, IPN and the Autonomous University of Sinaloa (UAS) are working on the modernization of the Subsidence Monitoring System in the Valley of Mexico, which will allow the collection, processing, interpretation and dissemination of the results of this work, both historical and recent.
Guadalupe Esteban Vázquez Becerra, professor and researcher at the Faculty of Earth and Space Sciences (Facite) at UAS, explained that the continuation of the project requires support from Conacyt to combine the GPS system with sensors, as well as meteorological stations to quantify subsidence in the Valley of Mexico over time.
In the publication released by Conacyt, Vázquez Becerra, assures that the monitoring of the sinking phenomenon in CDMX moved the researchers because of “the construction of the New Airport in Mexico City…. The idea is to help quantify how much it sinks, in real time, that is, to keep a timely record”.
Israel recalls how the September 11, 2017 earthquake in Mexico brought to light many problems. Such as the poor condition of many homes, especially in areas south of Mexico City. Xochimilco is a place known to tourists for its canals and mariachis; they call it ‘the Mexican Venice’. But it is also one of the areas with the greatest land subsidence, which causes sinkholes in the streets and problems in homes such as cracks. This is one of the consequences of the extraction of water from the aquifers, the so-called subsidence, which could put 1.2 billion people in the world at risk.
Researchers from the National Autonomous University of Mexico (UNAM) determined that water management has been the reason for land subsidence in many areas of Mexico City, as well as massive construction. Groundwater extraction began to grow, the studies say, and aquifers have been drained. The soil in the Mexican capital is very soft, porous and unstable, which increases the danger in the area.