Breaking news! Tonight, Mexico City (CDMX) was surprised by a micro-earthquake, which was felt mainly in the Benito Juárez borough. Where else was it felt? The tremor occurred this Monday, September 2, near the Valley of Mexico.
However, the National Seismological Service (SSN) reports that a micro-earthquake of magnitude 2.5 was also recorded in the Álvaro Obregón municipality, northwest of the municipality, during the night of Monday, August 2.
EARTHQUAKE Magnitude 2.5 Location 2 km NORTHWEST of V ALVARO OBREGON, CDMX 02/09/24 22:42:47 Lat 19.41 Lon -99.21 Pf 1 km
— National Seismological Institute (@SismologicoMX) September 3, 2024
Subsequently, two more earthquakes were reported with their epicenter in the Benito Juárez municipality, the first with a magnitude of 1.9 and the second with a magnitude of 1.4 southwest of the capital municipality.
EARTHQUAKE Magnitude 1.9 Loc. 1 km SOUTHWEST of BENITO JUAREZ, CDMX 03/09/24 00:13:18 Lat 19.40 Lon -99.17 Pf 1 km
— National Seismological Institute (@SismologicoMX) September 3, 2024
EARTHQUAKE Magnitude 1.4 Loc. 1 km SOUTHWEST of BENITO JUAREZ, CDMX 03/09/24 00:19:02 Lat 19.40 Lon -99.17 Pf 1 km
— National Seismological Institute (@SismologicoMX) September 3, 2024
What is a microseism? The reason why they are felt in CDMX
According to the UNAM Institute of Geophysics, a microseism is a small magnitude earthquake that occurs in a specific area and lasts very short, just a few seconds. These are generated by small ruptures inside the earth, located near the surface, at a depth of about four or five kilometers.
There are several reasons why Mexico City is prone to experiencing microseisms. When talking about these movements, it is highlighted that the country’s capital is located on the Pacific Ring of Fire, a subduction zone with high seismic and volcanic activity; however, other factors are also mentioned such as:
- The Valley of Mexico is built on ancient lakes. This type of soil, known as lacustrine, amplifies seismic waves, making tremors felt with greater intensity and duration.
- The extraction of water from the subsoil and large constructions have also caused an increase in these small movements.
- The presence of volcanoes in the vicinity of the country’s capital, such as those in the Sierra de Santa Catarina, also influences local seismic activity.
Why did the seismic alert not sound with today’s micro-earthquake?
Although hundreds of residents of the capital reported that the micro-earthquake of September 2 was felt quite strongly, the seismic alert was not activated. Why? According to the Mexican Seismic Alert System (
SASMEX
), the alert is issued only in situations where the earthquake represents a significant threat, and it does not detect local movements.
Another reason is that the alert is only activated if the earthquake has a magnitude greater than 5.0 and occurs less than 250 kilometers from the city.
