Strange noises in September cause confusion in Mexico after recent earthquakes.

The month of September has historically been significant for Mexicans, not only for the celebration of independence but also for the memory of tragic earthquakes that have left a mark on the country’s collective consciousness. The most remembered events are the earthquakes of 1985 and 2017, which have become synonymous with this month. However, in recent days, residents of several localities, including Naucalpan and the Benito Juárez borough, have reported an unusual acoustic phenomenon associated with microseisms: loud noises that many describe as explosions. As tremors have shaken the region, social media has been filled with recordings showing the moment of the shake followed by a loud noise, generating confusion and fear among residents. In Naucalpan, a video from a security camera reveals a calm scene interrupted by a loud sound, followed by movements in the surroundings. This type of event has led the population to question the nature of these sounds and whether they are related to the earthquakes. The National Seismological Service (SMN) has been aware of these movements, and despite some of them being of low magnitude, the explosive sounds have raised alarms among citizens. The most recent case occurred on September 5, when a magnitude 2.3 earthquake was recorded near Mexico City. The alert came 20 minutes after the event, leaving many without the opportunity to react appropriately. However, it is vital to clarify that the reported sounds are not indicative of a seismic phenomenon per se, but rather the result of rock fractures in geological faults. SkyAlert, a seismic alert platform, explained that these noises occur at the moment when the rock breaks during an earthquake, a phenomenon that is more perceptible in shallow-focus earthquakes, such as those that occur in Mexico City. But what is seismic noise? According to the National Autonomous University of Mexico (UNAM), seismic noise refers to recorded vibrations that do not originate from an earthquake. These noises can be caused by a variety of factors, including weather phenomena, vibrations from the monitoring equipment itself, and human activities such as traffic and heavy machinery. This context is crucial for understanding the perception that people have about what happens during tremors. Research conducted by Dr. Xyoli Pérez Campos from the Seismology Department of UNAM provides a broader framework for understanding seismic noise. During the most critical years of the COVID-19 pandemic, a notable decrease in seismic noise was observed in various parts of the world, including Mexico. This phenomenon was due to the reduction of human activity, which allowed seismic stations to capture clearer and less interfered signals. Dr. Pérez Campos clarifies that it is possible to distinguish vibrations generated by human activity within the spectrum of seismic noise. These vibrations, which range from 1 to 5 Hertz, show distinct patterns depending on the time of day: at night, activity decreases, while during the day, the hustle and bustle of urban life becomes more evident. It is important for the population to be informed about these phenomena and the differences between seismic noise and sounds associated with earthquakes. This not only helps demystify events that can cause panic but also allows citizens to have a better understanding of their geological environment. Education on seismic matters can be crucial for preparedness in the face of future earthquakes. The growing concern about strange noises during earthquakes is understandable, especially given the history of devastation that seismic phenomena have caused in Mexico. However, it is essential that information about these events is accurate and that scientific explanations are accessible to all. Science and effective communication are fundamental tools for the population to face the challenges that nature presents with greater confidence. Thus, while September continues to be a month remembered for tremors and tragedies, understanding what occurs underground and in the acoustic environment can help society cope with the fear and uncertainty that these phenomena provoke. Education and scientific outreach are key to resilience in a naturally active environment like that which characterizes Mexico.