In Mexico, three earthquakes of great magnitude have shaken the country on September 19 in three different years: 1985, 2017 and 2022. What some call a curse, for science is an unremarkable coincidence.
“The probability of two large earthquakes occurring on the same calendar date by pure chance is very high,” indicates an article published in the Journal of the Dissemination of Science of the National Autonomous University of Mexico (UNAM).
[A strong earthquake shakes central Mexico and forces the buildings of the capital to be evacuated]
One of the specialists who signs the text is the doctor in geophysics, Xyoli Pérez-Campos, a researcher at the UNAM Institute of Geophysics and the California Institute of Technology, who explained to Noticias Telemundo that this is because “Mexico is a country highly seismic.
In Mexico, an earthquake of magnitude greater than seven occurs almost every two years
(1.6 years to be exact) and in the 120 years of record, "several significant earthquakes have been reported on the same calendar day," he says.
The plates do not know about calendars.
They know that they are reaching a critical point and they break.
When it's their turn, it's their turn"
Xyoli Pérez-Campos seismologist
Although it is perhaps the best known date, September 19 is not the only one that is repeated.
"On April 18 we can find significant earthquakes in Mexico that have occurred in different years," says Pérez-Campos.
Among them, he cites two from April 18, 2002, one with magnitude 6.5 and another 6.0 in Guerrero;
12 years later, that same day but in 2014, there was a 7.2 earthquake, also in Guerrero.
Since 1980, at least "40 earthquakes have been large enough to be perceived by the population," Pérez-Campos wrote in a 2018 text signed by her and by fellow seismologist Diego Melgar on the specialized site The Conversation.
Only in 1995 three of magnitude greater than seven were registered.
In countries like the United States "eight earthquakes of these magnitudes have occurred since 1900", that is, one every 14.7 years, explains the article in the UNAM Science Popularization Magazine.
It trembles again in Mexico on September 19, the same day that the earthquakes of 1985 and 2017 occurred
Sept.
19, 202204:02
Earthquakes occur due to the movement of the tectonic plates of the earth's crust and due to the rupture that occurs when they no longer resist the effort and constant interaction.
“Plaques don't know about calendars”,
emphasizes Pérez-Campos.
“They know that they are reaching a critical point and they break.
When it's their turn, it's their turn."
Earthquakes and the birthday paradox
The UNAM magazine pointed out that, in the catalog of the National Seismological Service of Mexico, there are "at least 74 earthquakes of magnitude greater than or equal to 7.0" according to earthquake statistics since the early 1900s.
Two earthquakes have occurred on the same date in at least seven cases, he said.
[On video: A drone records the destruction of a bridge after a strong earthquake in Taiwan]
In networks circulates a data offered by José Luis Mateos, specialist in complex systems of the Institute of Physics of the UNAM, which establishes that "the probability that three earthquakes of more than 7 degrees are registered in a country in three September 19 is a by 133,225, that is, 0.000751%”.
Javier Santaolla, a researcher in physics and engineering, debated this analysis in a video on Instagram, assuring that "we are intuitively bad at calculating probabilities."
For him, the error is due to the fact that when calculating "they are not taking into account that there are 40 earthquakes in these 40 years, not just three, and the second mistake is that they are not testing all possible combinations."
Santaolla refers to what is known as the “birthday paradox”, which explains that in a group of 23 people there is a 50% probability that two of them share the same birthday, while in a larger group of 70, that probability is of 99%.
After trying all the possible combinations, he asserts, the possibility of three earthquakes occurring on the same day in different years "is 10%, a much less extraordinary percentage."
Are there similarities between the earthquakes of September 19?
The 1985 and 2022 earthquakes in Mexico are similar in terms of why the rupture originated, but they differ in magnitude and where their epicenter was, seismologist Pérez-Campos explained to Noticias Telemundo.
This Monday's earthquake was of magnitude 7.7 and caused two deaths in Manzanillo, Colima;
the one in 1985, which killed some 10,000 people in Mexico City, was 8.
"That difference that seems very small, of 1.3 units, is actually a difference of approximately 3.5 times the energy released, that is, three times larger," he explained.
[Using the phrase “damn 19” many Mexicans describe the day in September in which three earthquakes have occurred]
In the text published in 2018, she and her colleague stated that the 2017 earthquake, in which more than 300 people died, was “fundamentally different from the one in 1985” and from “most of the large earthquakes that occur in the country.”
Usually when two tectonic plates collide, one slides under the other and "follows a diagonal path deep into the Earth's mantle."
But with the 2017 earthquake, a shift in displacement occurred as the plate "suddenly and almost vertically dives into the Earth's mantle" causing a bending earthquake, in which something similar to what happens if we bend a piece of wood that resists until it breaks.
Is it possible to predict an earthquake?
There is no way to know in advance when and where an earthquake will strike,
seismologist Hadi Ghasemi and geophysics professor Phil R. Cummins said in a 2021 article in The Conversation.
"No one has ever found a reliable and repeatable indicator that an earthquake is about to occur," they said.
Residents of Mexico's capital say the tremor was "super terrifying"
Sept.
19, 202206:31
The seismologist says that it is impossible to attract earthquakes with our thoughts, as some of the wildest theories she has heard say.
The plates move due to the internal dynamics of the Earth and "these are gigantic efforts that are occurring" for this reason "it is impossible for external phenomena and our own minds to have the will to move those brutal masses of land".
It is not possible to predict them, much less attract them.
To know exactly when one will happen "we would need a very detailed model of all the rocks in the Earth's interior and an understanding of how they respond to tectonic stresses."
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