Mexico City // A powerful quake strikes off the Pacific coast of Mexico. In seconds, radio transmissions, speakers and smartphone apps blare warnings to the city’s 20 million people before the ground shakes.
After the loud “seismic alert” alarm, city residents have up to a minute to flee their buildings.
But the technology was not available on September 19, 1985, when an 8.1-magnitude coastal quake rocked the city, killing thousands and crushing buildings.
It takes more than a minute for seismic waves to hit the city hundreds of kilometres away but when they do, buildings start moving because the soil below, a former lake bed, is soft.
When Mexico on Saturday marked the 30th anniversary of the quake, the warning systems were to be switched on for a national drill.
For 20 years, a civil group known as Cires has provided the city with a system that automatically interrupts radio broadcasts and triggers alarms inside buildings, thanks to 100 sensors placed along the west coast. This year, for the first time, the alarm will sound on 8,200 street speakers.
The surge of smartphone technology also means residents can receive warnings in the palm of their hands with apps such as SkyAlert and Alerta Sismica DF.
Within two seconds of a quake hitting, SkyAlert’s sensors send a broadband signal to phones, triggering a loud sound with a voice that repeats “seismic alert” and a message telling how strong the quake is. Launched in 2013, the app has 3 million users.
“This type of system carries great responsibility,” said SkyAlert founder Alejandro Cantu, 29.
SkyAlert split from the Cires system, which uses radio waves, last year after Mr Cantu travelled to Japan and brought back sensor technology for his app.
In May, the company charged users 59 pesos (Dh12.85) a year to personalise their alerts, gaining 30,000 paid customers so far.
While SkyAlert quickly became a popular app, it jolted its customers in July last year with a false alarm. At the time the app was still linked to Cires, which Mr Cantu blames for the error, but Cires says it was SkyAlert’s doing.
US experts travelled to Mexico last week to learn more about the system as they develop something similar for the West Coast.
“When we talk about the importance of an early-warning system, we hold up the Mexican and Japanese systems as examples of functioning systems,” said Jennifer Strauss of Berkeley Seismological Laboratory in California.
* Agence France-Presse
