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With the purpose of alerting the population of seismic activity with epicenters in central Mexico, Armando Cuellar, PhD student at the Geophysics Institute of Mexico’s National Autonomous University (UNAM) has developed an algorithm capable of emitting warnings 8 seconds ahead for earthquakes such as the one that struck Mexico City on September 19, 2017 .
The software senses the telluric movement barely three seconds after it is generated
and is able to determine whether or not the alarm should be activated in the first place.
“An 8-second head start may not seem like much when compared with the whole minute warning issued whenever the epicenter is located in the shores, but those seconds are very important for schools, hospitals, security systems, and the general population to take precautions ,” explained Dr. Gerardo Suárez, Cuellar’s thesis director .
An earthquake may generate two types of waves similar to those produced when a water drop strikes a surface: Body waves travel through the interior of the earth and have a higher frequency than surface waves, which is why they spread much faster and are perceived with a loud and deep sound. Surface waves travel only through the Earth's crust; they can easily be distinguished on a seismogram but are much more dangerous than body waves due to their effects on structures and buildings.
The doctor from UNAM explained that the seismic alert currently in use is working with algorithms designed to detect both types of waves at the same time. However, last year’s earthquake was originated at the center of the national territory and at a greater depth, which is why the second wave took so long to reach the sensor, and the alert was not activated on time.
“Our algorithm is able to determine or evaluate the magnitude of the event with far less information: Only one of the seismic waves is enough for the program to decide whether or not the alert should be activated, offering an earlier warning mechanism,” stressed Suárez.
The investigator added that the alarm for 19S was activated shortly after the earthquake started because the epicenter was very close to Mexico City .
The algorithm was mainly developed by Cuéllar based on the information of 76 accelerographs placed at 25 monitoring stations for seismic activity with 40 kilometer depth .
The software was implemented by the Center of Instrumentation and Seismic Evidence (CIRES) which is in charge of operating the seismic alert.
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