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Mexico’s earthquake early warning system gave some over a minute’s notice

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The U.S. has been working on a similar alert tool for a decade—where is it?

View of a street at the eastern area of Mexico City after a 8.1 earthquake on September 8.
View of a street at the eastern area of Mexico City after a 8.1 earthquake on September 8.
ALFREDO ESTRELLA/AFP/Getty Images

Mexico was rocked by an 8.1 earthquake last night, the country’s most powerful quake in 100 years. At least 32 people have been reported dead, a number that may rise in the coming days. But the impact of the disaster may have been substantially lessened thanks to Mexico’s effective early warning system—a life-saving tool that the equally quake-prone Western U.S. still hasn’t implemented.

Thanks to a series of sensors that are installed along Mexico’s fault-riddled West Coast, the early warning system can deliver an alert within seconds of an earthquake. In addition to an app that residents can download, the alert is broadcast on television and radio, and over speakers installed in public areas, schools, and buildings.

The early warning system, known as Sistema de Alerta Sísmica Mexicano or SASMEX, gave some Mexicans over one minute’s warning about last night’s quake, which hit at 11:49 p.m. local time and was epicentered off the Pacific Coast near the Guatemalan border. Mexico City, which is located about 320 miles away from the epicenter, had more than 86 seconds to prepare for the impending shaking.

A map of Mexican cities and how much time they had to prepare for the earthquake thanks to the early warning system.
SASMEX

Mexico’s government pushed for the development of an early warning system after a devastating 1985 earthquake—an 8.0—that may have killed up to 40,000 people and leveled entire Mexico City neighborhoods. By 1991 the country had the public-announcement system in place, and in 2013 it launched the smartphone app, which now has millions of users.

"When we talk to people about the importance of an early-warning system, we hold up the Mexican and Japanese systems as examples of functioning systems," Jennifer Strauss of the Berkeley Seismology Lab said in 2015.

The United States Geological Survey and a coalition of partners has been developing a similar alert system for the past decade called ShakeAlert, but it won’t be operational until there’s funding to install the full network of sensors.

In 2016, Congress allocated $10 million for the early warning system, with the state of California kicking in an additional $10 million. But earlier this year, the $38 million needed to get the system up and running was slashed from the federal budget. (It now seems like funding may be allocated as planned—pending budget approval.)

A prototype of the U.S.’s ShakeAlert app, which may be available as soon as next year.

In addition to giving residents a heads up—and, in the case of last night’s quake, a chance to get out of bed and take cover—the early warning system can also be used to automatically shut down transit systems and electrical infrastructure, preventing secondary disasters like derailments and fires. In fact, San Francisco’s BART system already uses the beta version of the early warning system to slow or stop trains during tremors.

The system is also essential for warning residents about aftershocks, which can sometimes be more deadly than the initial quake, because people are moving through weakened or damaged buildings.

What makes an early warning system effective is not just about quickly dispersing the scientific information about a quake; there’s also a field of practice built around exactly how to distribute that information to the public in a way that will prevent loss of life. In the U.S., the team working on the ShakeAlert beta include not just seismologists but behavioral scientists, communications experts, and graphic designers who have to decide how much data to give out.

Due to the number of buildings that were destroyed in the 1985 earthquake, most residents of Mexico City use the early warning time to get outside, which is why the post-quake photos you’ll see from last night feature people in their pajamas wandering the streets. That’s one of the biggest challenges with crafting emergency alerts, since the U.S. would want residents to take approved earthquake protocol—drop, cover, hold on—instead of sending them running.

Early warning systems must also go hand-in-hand with seismic structural upgrades in order to save lives. Although Mexico City has invested in quake-proof infrastructure and stricter building codes, these same improvements have not been made in many rural communities. Which is why the West Coast states of Chiapas and Oaxaca—where the shaking was the strongest and residents had the least amount of warning—seem to have sustained the bulk of the devastation in last night’s quake.

On the other hand, an early warning is a simple tool that can help someone quickly evacuate what is known to be a substandard building—provided they get the alert.

This part of Mexico has now experienced the unthinkable—two 8.0 earthquakes in the span of 32 years—yet the country has taken great strides to protect its residents over the last three decades. The Western U.S., particularly in the Pacific Northwest, which is at risk for the largest earthquakes in the country, is long overdue for the Big One, and scientists know an early warning system is the best way to lessen its impact. It’s only a matter of time until it’s our turn—and right now, we’re not ready.