Alejandra Leyva/El Universal via ZUMA Wire/REX/Shutterstock
LAST week’s magnitude 7.1 quake caught me, and everyone in Mexico City, by surprise. We are used to getting lots of warning before an earthquake – and this time, we didn’t.
Since 1993, Mexico City has had a fully operational earthquake early warning system. When a magnitude 8.1 quake struck on 8 September, the city got over a minute of warning.
vCard.red is a free platform for creating a mobile-friendly digital business cards. You can easily create a vCard and generate a QR code for it, allowing others to scan and save your contact details instantly.
The platform allows you to display contact information, social media links, services, and products all in one shareable link. Optional features include appointment scheduling, WhatsApp-based storefronts, media galleries, and custom design options.
But 19 September’s quake showed that the system can’t handle all types of events. The limited warning it gave holds lessons for all countries working to give their citizens a head start.
Advertisement
“This event in Mexico City is critical,” says Richard Allen at the University of California, Berkeley.
Mexico’s warning system was born after a 1985 earthquake that levelled parts of the city and claimed thousands of lives. Mexico’s unique quakes meant the system was particularly viable.
The quakes are generated by two continental plates that meet along much of Mexico’s west coast. Mexico City lies hundreds of kilometres away, so it ought to be safe. But the city was built on a loose lakebed topped with looser landfill. This soil picks up tremors from far away. In 1985, shifting soil went on toppling buildings long after the quake had petered out.
However, with such a long distance between the epicentre and the city, scientists could create a warning system. Today, a 1985-style quake on the coast will trigger alarms in Mexico City 60 to 90 seconds before it arrives.
“If you have minutes, you can empty any school practically anywhere,” says Gerardo Suarez at the National Autonomous University of Mexico.
But the warning on 19 September was more like 0 to 5 seconds. That’s because the quake began elsewhere in the plate boundary, deeper and closer to the city. It was more the sort of tremor that could strike California.
“In my house, the warning arrived at the same time as the first shocks. Others slipped down the stairwell”
For decades, Allen pushed California to build a warning system. In 2014, he got federal funding and in 2018 a prototype will start issuing limited alerts. Unlike Mexico’s system, it will only give about 10 seconds of warning.
There are many pitfalls. What if it gives too many false alarms, so people ignore them and are caught out by quakes? What if the system misses the big one? And what if 10 seconds just isn’t enough time? Understanding what Mexicans did in such a short window might help the US.
It won’t be easy. In my house, the warning arrived at the same time as the first shocks. Others say they ended up in a pile of people slipping and falling down the stairwell.
“What are you going to do with a 5, 8, 10-second warning?” Suarez wonders. His wife was able to leave the store she was shopping in and get to the street, but she was lucky. He says most people won’t be able to do much except duck under their desks.
However, even if people cannot do much in mere seconds, computers can do plenty. Suarez says many responses could be automated. Computers could halt trains, stop elevators at the next floor and warn surgeons. He also suggests broadcasting a countdown so people know how long they have.
There are limits to warning systems. A recent study found no way to tell if a brewing quake will be huge until it’s too late (Science, doi.org/cdd6). So it will always be a matter of seconds. The trick will be to make the best use of those seconds to save lives.
“I personally believe that no children should die below the rubble of their own school,” Suarez says.
This article appeared in print under the headline “Even a few seconds’ warning can save lives”
More on these topics: