"Three micro-seisms shake CDMX: challenges of the seismic alert system"

On the night of September 2, residents from various neighborhoods in the Álvaro Obregón and Benito Juárez boroughs of Mexico City felt the impact of three microseisms that shook the capital. The strongest of these quakes reached a magnitude of 2.5, with its epicenter located to the northeast of the borough governed by Lía Limón, in an area near the Plateros-Mixcoac fault. At 10:42 PM, the National Seismological Service (SSN) confirmed the first seismic event, followed by another at 12:42 AM on September 3, with an epicenter to the southeast of Benito Juárez, which registered a magnitude of 1.9. A third microseism was reported minutes later with a magnitude of 1.4, also in this same area. Despite residents feeling the tremors, authorities reported no material damage or injuries. The Secretariat of Integral Risk Management and Civil Protection (SGIRyPC) communicated through its account on the social media platform X that they maintained contact with the various units of each borough, paying special attention to those closest to the epicenter. This coordination is part of the safety and prevention protocol implemented in the capital for any seismic events. The Command, Control, Computing, Communications, and Citizen Contact Center of Mexico City, known as C5, also joined the monitoring and communication efforts, clarifying that the seismic alert was not activated. This is because the epicenter of these quakes was located within Mexico City itself, which poses a challenge for the alert system that relies on detecting earthquakes in peripheral areas to issue an early warning. The lack of activation of the seismic alert highlights the limitations of the Mexican Seismic Alert System, which, as experts explain, requires a minimum amount of time to assess the impact of an earthquake before issuing a warning. In the case of seismic movements occurring within the capital, the time it takes for seismic waves to reach nearby areas is so brief that it does not allow the system to issue an effective alert signal. This situation raises concerns among residents, who may feel vulnerable to lower magnitude quakes that can still be felt. Scientists from the National Autonomous University of Mexico (UNAM) have pointed out that microseismic activity in the capital could be related to water extraction carried out to supply the megalopolis. The city obtains approximately 56% of its water from 976 wells distributed across various areas, which could alter geological conditions and contribute to seismic activity in the region. This context underscores the need for a comprehensive approach to water management and urban infrastructure in the capital. Additionally, the Government of Mexico has indicated that the Seismic Alert System is based on data collected by the Center for Instrumentation and Seismic Recording (CIRES), which focuses on detecting significant earthquakes in the Guerrero Gap. This system, which has proven effective for quakes occurring outside the capital, faces significant limitations due to the incessant local seismic activity. The recent series of microseisms also highlights the importance of preparedness and seismic education among the population. Although the recorded movements were of low magnitude, a sense of unease is present in a city that has lived with the memory of devastating historical earthquakes. Prevention and knowledge are essential tools for adequately addressing any seismic eventuality. In this context, local authorities are called to strengthen their communication and prevention protocols, as well as to promote a culture of preparedness for earthquakes among the population. It is crucial for citizens to understand the measures to take in the event of an earthquake and to stay informed about the seismic activity occurring in the capital. Finally, this is an opportune moment for both citizens and authorities to reflect on the need for a more robust and efficient alert system, one that not only serves to detect large magnitude earthquakes occurring outside but can also provide useful and timely information in the case of seismic movements happening within the city. Life in the capital, one of the largest in the world, requires proactive measures to ensure the safety and well-being of its inhabitants.