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Will microseisms be repeated in Mexico City? A seismologist sees it as possible

2023-12-17T22:01:06.852Z

Highlights: Víctor Cruz, a seismologist at UNAM, explains that the faults under the city are slipping "slowly" at the moment. Regarding the possibility of an earthquake of magnitude greater than 5 in the capital, the scientist concludes that it is difficult but "not impossible" A "swarm of microseisms" may be affecting Mexico City, according to seismologist Víctor Manuel Cruz Atienza. These low-magnitude earthquakes occur under the floor of the city, some of them at a depth of only one kilometer.


Víctor Cruz, a seismologist at UNAM, explains that the faults under the city are slipping "slowly" at the moment. Regarding the possibility of an earthquake of magnitude greater than 5 in the capital, the scientist concludes that it is difficult but "not impossible."


By EFE

A "swarm of microseisms" may be affecting Mexico City, according to seismologist Víctor Manuel Cruz Atienza, after the numerous tremors experienced in recent days in the Mexican capital. Meanwhile, citizens are wondering about the real risk of these events.

The expert from the National Autonomous University of Mexico (UNAM) said that "it is possible" that more events of this nature could occur in the coming days and even weeks.

Víctor Manuel Cruz Atienza, specialist in earthquake physics. Gustavo Huerta / EFE

The inhabitants of Mexico City live with the worry of not being able to count on the warning of seismic alarms. These low-magnitude earthquakes that occur under the floor of the city, some of them at a depth of only one kilometer, are not intense enough to set off alarm bells.

Cruz Atienza explained that the microearthquakes in May of this year and those of this week have occurred in the south of the city, where in 1981 "there was a swarm of earthquakes."

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These phenomena are not new. There are works published in 1971 documenting local earthquakes between 1909 and 1969.

For Cruz Atienza, the faults under the city are slipping "slowly" right now. His hypothesis is supported by "satellite evidence."

One of the characteristics of micro-earthquakes that most frighten the people of the capital is the violence with which they manifest themselves at first, which is explained by the acceleration they produce.

The microearthquake recorded at Panteón Dolores on June 17, 2019 had a maximum acceleration of 310 gals (981 gals equals the acceleration of gravity).

Cruz Atienza compares this figure with the 34 gals recorded, also in solid rock, of acceleration in Mexico City after the devastating earthquake of 1985. The difference is due to the proximity of the epicenter of the microseisms, just below the ground.

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For the UNAM expert, very high accelerations do not imply a great risk "in principle", as they are "very brief".

People outside their homes after hearing the seismic alert in Mexico City, on December 7, 2023.Sashenka Gutierrez / EFE

The microearthquake of May 2019 and the concern it raised raised doubts about whether the works on line 12 of the metro were responsible for the events.

For this reason, the then head of government of Mexico City, Claudia Sheinbaum, "someone afraid of earthquakes" according to Cruz Atienza, unified the seismological network of the Valley of Mexico. Today the capital has about 180 stations that monitor local activity.

However, it has not been possible to demonstrate the relationship between the works and microseisms. Over the years, there have been other theories about the causes of them: a 1991 report pointed to a correlation between "increased rainfall and microseisms," Cruz Atienza recalls.

"A more delicate issue was that from the 2019 microearthquake we did a published study that postulated a larger scenario of an earthquake with an epicenter in the same city of magnitude 5, about 800 times larger than the one on Thursday. We checked what the acceleration would be in the central lake area of Mexico City. Estimates suggest that this hypothetical earthquake compared to those of 1985 and 2017, for no height of the buildings, the acceleration would be greater than that of those earthquakes in the soft sediments of the capital," said the seismologist.

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Mexico City's building code "drawn up after the 1985 disaster" contemplates that buildings can withstand a magnitude 4.7 earthquake under the city, clarifies Cruz Atienza, who adds that "urban developments without legal control on the slopes of the great Mexican city could be in danger," in the event of a nearby microseism.

On whether an earthquake with an epicenter in the capital greater than magnitude 5 can occur, the scientist concludes that it is difficult but "not impossible."

Source: telemundo

All news articles on 2023-12-17

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