“Guerrero gap”, possible cause of the September earthquake

The so-called “Guerrero gap” can cause a devastating earthquake at any time that would affect a large part of Mexico, according to research by geophysicist Víctor Manuel Cruz Atienza.

The earthquake of the past, September 7, 2021, in Mexico, of magnitude 7, could be due to a earthquake slow generated in the “Guerrero gap” that has been accumulating energy for more than 100 years and that runs the risk of occurring again with greater intensity.

Víctor Manuel Cruz Atienza, geophysicist, seismologist from the National Autonomous University of Mexico (UNAM) and head of the Mexican-Japanese team that has been studying the dreaded gap for five years, supports this hypothesis based on data collected by the institution’s GPS network.

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Dr. Cruz Atienza is at a decisive moment because he needs to find the funding to organize an expedition that allows scientists from UNAM and the University of Kyoto to collect the seismometers from the ocean floor.

In these seismometers (OBS, for its acronym in English) are the measurements made since 2019 of the activity of the “Brecha de Guerrero”, a maritime seismic zone 130 kilometers long that begins in Acapulco and that for more than 100 years it does not cause a major earthquake.

Its accumulated energy could cause, according to Cruz Atienza, an earthquake that affects a large part of the country, including the capital, in the Valley of Mexico where more than 20 million people live.

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If it is confirmed that what happened during the two months prior to September 7 was a slow earthquake in the “Guerrero gap”, it would mean that it releases energy silently, which would explain the absence of earthquakes of great magnitude.

On the contrary, it could indicate the proximity of the break that releases the Accumulated energy. Picking up those instruments with the batteries at their expiration date is essential to find out what happened on September 7.

Effects of slow earthquakes

“A slow earthquake is a landslide in a geological fault that does not generate seismic waves,” explained Dr. Cruz Atienza.

Slow earthquakes were discovered in 2001 and in Guerrero they normally occur every 3.5 years.

“We want to know more about the implications of this phenomenon in potentially devastating earthquakes,” he said.

In 2016 the researcher and his team already predicted the effects of the strong earthquake that caused hundreds of deaths in September 2017 in Mexico.

For this reason, the journal “Nature” included the researcher in the group of the ten world personalities that marked 2017.

These days, the scientist sends letters to the directors of the institutions involved in the binational cooperation dedicated to the study of the “Guerrero Gap”, to carry out an expedition oceanographic It is urgent that he retrieve the seven OBS belonging to the “Earthquake Research Institute” of the University of Tokyo.

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The pandemic of the Covid-19 It has prevented, among other reasons, its recovery initially scheduled for November 2020.

Cruz Atienza explains that it is “an emergency with transcendence in international relations between Mexico and Japan” since in addition to the OBS, they have other stations that are measuring the hydrostatic pressure at the bottom of the sea to estimate the vertical deformation of the continent.

Urgent expedition

“We are talking about millions of dollars and five years of uninterrupted efforts by both nations,” stressed the scientist, insisting on the “urgency” of recovering the OBS in 2021 because their batteries are about to run out, and with them, the possibility of ” better understand the seismic potential of the gap for the prevention of future disasters “.

Once Cruz Atienza and his team collect the instruments, they will know, among other things, where and how the slow earthquake that could cause the last earthquake in Acapulco occurred.

“For the first time we have enough evidence to think that a slow earthquake occurred in the middle of the Guerrero seismic gap and offshore,” he added.

The “Guerrero Gap” has spread to the southeast and accumulated energy for decades. The catastrophic scenario is that an earthquake suddenly releases all that energy.

To avoid this, 32 earthquakes of magnitude 7 have to occur in the same place to release the energy of one of magnitude eight. So many earthquakes would take decades if not centuries to occur.

From that perspective, “a magnitude eight one is more likely to occur in an uncertain but near future,” Cruz Atienza said.

If the slow earthquake prior to the Acapulco earthquake is confirmed with ocean data, it would be the first observation of this phenomenon in Mexico using instruments. geodesics submarines.

“This would allow us to better support the hypothesis that we have built in recent years that this specific segment of the gap, between Papanoa and Acapulco, has a very particular mechanism that would explain why so much time has passed since the 1911 earthquake,” said the scientific.

The 1911 Guerrero earthquake occurred on December 16 near the coast of Guerrero and had a magnitude of 7.5 degrees.

The earthquake was felt in much of the country and in the two minutes of duration there were 28 deaths.

Some of the largest earthquakes since then have been in 1957 (Acapulco), 1985 (Michoacán), 1995 (Colima-Jalisco) and 2017 (Tehuantepec).

jgt / melc

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