Unlike the quake two weeks ago, whose epicenter was in the state of Chiapas, the system of alarms that Mexico has to warn the population did not work for Tuesday's earthquake.
The reason is simple: on Tuesday the epicenter was in Puebla, about 100 kilometers from Mexico City and the proximity prevented the alert was activated in time to allow the population to take their precautions before the earthquake occurred.
"We have to remember that no earthquake alert works for earthquakes that are so close," Xyoli Pérez Campos, head of the National Seismological Service, told El Pais newspaper.
Carlos Valdés, director general of the National Center for Disaster Prevention (Cenapred), also added that "the depth, so low, has made the propagation almost immediate and felt practically at the same time that the movement was detected by the sensors ".
Mexico's seismic alert system is composed of a series of sensors located along the Pacific coast that detect seismic waves and emit an alarm through 8200 megaphones deployed in the capital.
The alarms allow to evacuate the high buildings of the Mexican capital, the schools, ministries and diverse offices. The transmission of radio and television is also interrupted.
The alarms give a time of between 30 seconds and one minute, before the movement begins, to allow the population to be sheltered.
The system has been operating since 1993, after the 1985 earthquake in which more than 10,000 people died.