The Michoacan earthquake won't reawaken Popocatepetl

For more than a year Popocatepetl has presented a low activity rate, with fewer ash emissions. The arrival of this dust to Mexico City occurs frequently because it is regulated by wind direction. The population is advised to pay attention to the recommendations.

The Michoacan earthquake won't reawaken Popocatepetl
Popocatépetl is not expected to become active again because of the earthquake in Michoacán. Credit: DGCS-UNAM

The Popocatepetl volcano is in a low period of activity and the ash emissions generated yesterday, September 19, are equal to those released in recent years, so it is unlikely that the recent earthquake in Michoacan will increase its activity, agreed UNAM experts.

Sergio Raúl Rodríguez Elizarrarás, from the Institute of Geology, and volcanologist Robin André Campion, from the Institute of Geophysics (IGEF), highlighted that emissions are registered within the usual parameters reported daily by the National Center for Disaster Prevention (CENAPRED).

Rodríguez Elizarrarás detailed: although not every day there are earthquakes like the one on September 19 of the current year, of magnitude 7.7, the behavior of Popocatépetl has been regular, and the report of a possible ash fall in some Mexico City municipalities, had no direct relation with the tremor.

"This happens quite frequently because it is regulated by the direction of the predominant wind, in this case, the wind that makes the ashes come to Mexico City goes to the northwest, something common in this summer season; in the winter season the winds go to the east, and the city of Puebla is the most affected by these phenomena", explained the specialist in the study of the Mexican Volcanic Belt.

The doctor in Sciences considered that the concern of the population was derived from the coincidences for registering an earthquake, on day 19, after a drill, and although there are not always this type of coincidences, it influences the mood of the people.

Robin André Campion agreed with him, who explained that for the last two years or so, the colossus has presented generally low activity, with fewer ash emissions, and fewer explosions, and has not experienced the growth of large lava domes, as occurred from 2011 to 2020.

This indicates that the structure has received little or limited magma and although "since mid-August, it has had a little more ash exhalation and small explosions, the media attention that the ash emission received is surprising because these emissions are daily at the volcano," he commented.

Some time ago, Servando de la Cruz Reyna, a researcher at IGEF, suggested the existence of a relationship between earthquakes of great magnitude and the behavior of the Popocatepetl volcano, Robin Campion collaborated with Thomas Boulesteix -who completed a postdoctoral fellowship at UNAM and now occupies a position at the Spanish National Research Council- on this theory and proposed an index that reviews factors such as distance, fault size, gas emissions and ash production, which was published last August in the Bulletin of Volcanology.

This could be observed in the next weeks, because the correlation between the earthquake and Popocatepetl's activity is not immediate, clarified the researcher.

"The value of the parameter that we have proposed to see if an earthquake can or cannot influence the activity of the volcano is marginally favorable for this earthquake (19/09/2022) to increase the activity of the volcano; it would have been more categorical if the earthquake had been larger or closer," explained Campion.

To exemplify how the seismic influence on the activity of the colossus has been, Campion and his team reviewed the records of earthquakes in the last 26 years, information that was compared with the activity of the volcano and, according to the data, that of 2017 (whose epicenter was in Chiautla de Tapia, Puebla) reached a value of 4 in terms of its influence on the colossus; while that of 1985 (also with epicenter in Michoacán) reached a valuation of 2.3.

To the above must be added that Popocatepetl's activity is more determined by its magmatic state, that is, if it has recently injected magma (as it makes it much more active with constant emissions of lava and ash), but currently all the monitoring carried out indicates that Don Goyo's magmatic feeding is low and this reduces, even more, the possibility that the last great earthquake has any influence on its activity, he said.

As to whether the proposed index can be applied to other types of volcanoes, especially Colima, Campion explained that Colima is closer to the epicenter, but it has been observed in the last 30 years that it has a much slower response rate.

The Colima volcano at this moment has less activity than Popocatepetl and although the influence index of this earthquake reaches approximately 2 (very high), this activity could manifest itself in one or two years, especially if it is considered that the 1985 earthquake influenced 1.2, but it was not until the end of 1986 when it reactivated.

The experts reiterated that during this season the rains wash the ashes into the atmosphere (precipitation carries them to the ground near the volcano), so they do not usually reach the Mexico City area. It is not possible to predict exactly when it will reactivate, it has been producing ash for 27 years and will continue to do so, so the population should remain attentive to the recommendations of CENAPRED and the corresponding authorities.