In Mexico we have the necessary technology to know how much damage will cause an earthquake, the type and magnitude that is, by areas and category of buildings.The government, however, has not shown interest in investing in it.In comparison, the atlas of dangers and risks that the National Disaster Prevention Center (Cenapred) and Civil Protection of the CDMX are barely an old -fashioned collection of maps.

This technology exists thanks to the fact that, for more than 25 years, the insurance sector has financed it, but it has not been used to prevent tragedies such as those of people who lost their lives, their relatives, and their heritage during the earthquakesSeptember 2017.

This is the story of a technological advance that could save lives in one of the most seismic risk cities in the world.

What do you do when you see your home discard?

"You cry," Anel Rosado García replies, one of the owners of the departments of Tlalpan 550."Inside your house is everything.And outside those sixty square meters there is nothing ".

Despite having less than seven years of being built, the departments were uninhabitable after the earthquake of September 19, 2017.Rosado, her husband and her 10 -year -old son went from being owners to tenants.After losing their heritage and all their belongings, they rented a room to live.Two weeks later, when she returned to work in La Segob, she had no clothes to wear.“I bought five skirts and five shirts, and every day was washed in the bathroom sink.Also the uniform of my son, who as only one had to wash daily."

Rosado is one of millions of victims of Mexico City for the earthquake of magnitude 7.September 1, 2017, which left almost 16,000 buildings with damage, more than 40 collapsed buildings and 228 dead.It has not been far from the most harmful that the Mexican capital has suffered.The earthquake of magnitude 8.1 of 1985 killed more than 10,000 people, threw about 400 buildings and caused damage to about 3,000 more.

The experts determined that most of the buildings that collapsed in the earthquake last year were old constructions that did not comply with the construction standards after 1985.The fact is that there was technology to know what type of buildings were at greater risk, even before that day trembled that day.

The foolishness of founding a city on a lake

Six years of the 1985 earthquake and Cinna Lomnitz, an engineer and geophysic expert in soil mechanics, had already passed, wrote the following in Nexos magazine: “We believe we understand why buildings fall in the Valley of Mexico.We need to know why there may be waves in solid land.The answer is perhaps simpler than we imagine: we are not on solid land. El Valle de México fue un lago y, desde el punto de vista del sismo, lo sigue siendo".

We must admit that Mexican geophysics and engineers have since advanced in the knowledge of the seismic response of the land and the buildings of the Valley of Mexico. Ahora, por ejemplo, saben por qué los sismos se amplifican cuando entran a la llamada “zona blanda" de la Ciudad de México y tienen un mejor entendimiento de por qué duran tanto, y sobre todo, cómo construir edificios robustos que los resistirán.

“El peor lugar para construir una ciudad, es la Ciudad de México", dice Luis Quintar Robles, geofísico responsable de la Red Sísmica del Valle de México.The megalopolis is built on the muddy ground where the Texcoco lake was once, on which the great tenochtitlán floated.

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Since the time of the colony they already knew about the inconveniences of building in these lake land.In the first decades of the seventeenth century, the cosmographer and engineer Enrico Martínez was sent by the crown to New Spain to solve the problem of frequent floods of the city.What Martínez suggested was sensible: to move the city to the Lomas area and leave the lake area for gardens and green areas.

Instead of attending the recommendation, the viceroy chose to sponsor a gigantic engineering project to make a drain for the city, and commissioned Martínez.Bad luck wanted that on September 21, 1629 a flood that lasted 40 hours fell.For five years, the city was flooded under two meters of water.As since then the Viceroyes did not take care of their mistakes, Martínez went to the prison accused of negligence and Mexico City continued where she was founded.

The city has not only continued flooding for centuries and it has always been a challenge to build buildings that sink on the mud.The biggest problem of having built the city about what were lakes became evident after 1985: this soil makes earthquakes even more devastating.

After the earthquake of September 19 of that year, Jorge Flores Valdés, researcher at the Institute of Physics at the National Autonomous University of Mexico (UNAM), realized that the destruction pattern was concentrated in the Lagos area, and thatAlternate high and low devastation areas seplanted by just some apples. Considerando que el suelo en algunas zonas es en volumen 90 por ciento agua, “se volvió evidente que las ondas sísmicas se habían propagado como ondas de sonido en agua".

Flores, which is theoretical and non -geophysical physical, used classical physics equations to model very real problems: describe the pattern of earthquake destruction. Su trabajo, “Posibles efectos de resonancia en la distribución de daños por sismos en la Ciudad de México" (en inglés en el original), fue la portada de la revista Nature en 1987.

The work of Flores was one of the former who equated the resonance of the Valley of Mexico to a bowl of water whose surface is stirred with the earthquakes.In that aspect there have already been many advances.Today, Víctor Cruz Atienza, a seismologist at the Institute of Geophysics of the UNAM, has other models to describe how the earthquakes horizontally and vertically spread in the sediments of the Valley of Mexico.

With them he explains why seismic waves intensify when they reach this region, why they are amplified up to 500 times when they pass from the ground firm to lake sediments, and why they last between 200 and 300 percent more than on the mainland.

In fact, Cruz Atienza coordinates a research project to monitor the so -called Guerrero seismic gap, which is an area 250 kilometers long where a significant earthquake has not occurred in more than 60 years.Due to the energy that is accumulating there, because they have not unleashed tremors strong enough to release it, seismologists expect an earthquake of magnitude greater than 8 degrees to occur.

This area is about 300 kilometers from Mexico City: 150 kilometers closer than the epicenter of the tremor of 1985.The closer to the epicenter is the city, the intensity is greater;That is why the magnitude 7 earthquake.September 1 was in some more intense aspects than 8.0, 1985, as his epicenter was just 120 kilometers from the city.

UNAM seismologists estimate that the accelerations of a tremor in that gap when touching the soft area of Mexico City will not only be more intense than the 7 -earthquake of 7.September 1, 2017, but would be two to three times stronger than those of 1985, particularly for buildings of more than 10 floors.They also estimate that the duration will be greater than those earthquakes: about three minutes in their intense phase.

Rescue engineering

Fortunately, Mexican engineers for many years have perfected the science of building resistant buildings in these conditions. “Los edificios nuevos dañados no debieron sufrir daños si hubieran seguido las reglamentaciones modernas", dice Edgar Tapia, ingeniero sísmico estructurista de la Universidad Autónoma Metropolitana, quien participó en brigadas voluntarias de revisión de inmuebles después del sismo del 19 de septiembre de 2017.

After 1985, the Construction Regulation was updated to divide Mexico City into three different areas based on the characteristics of the land (lake zone, transition zone and Lomas area), and after 2004 they divided it into six to six todivide in four regions to the Lake Zone.

From the new December 2017 regulation, the subdivision is so thorough that the designer can obtain a particularized design spectrum practically every 100 meters, where seismic demands can be obtained.This design spectrum, in broad strokes, is what allows to know what forces the building should resist based on its height and location. Tapia lamenta: “Ya teníamos estos lineamientos listos para publicarlos quizás desde 2016, pero no fue sino hasta después del sismo que las autoridades se apresuraron a actualizar el reglamento".

Read the full note in the new Newsweek edition in Spanish