Mexico’s second major quake in as many weeks inflicted death and destruction across the country with more than 200 dead, and the toll still expected to change.  Yet Mexico City, and several cities in its alert network, have one thing to give solace: an early warning system to avert even greater tragedy when earthquakes strike. 

The seismic warning system in place during the most recent magnitude-7.1 quake on Sept. 19, which had its epicenter about 75 miles from the country’s capital, successfully gave people crucial seconds to flee vulnerable buildings, and prepare for the worst.  In video from Mexico City, which saw the highest casualties in Tuesday’s quake, early warning sirens blare for at least 20 seconds before the shaking begins. 

The system exists because a 1985 earthquake in Mexico City left more than 5,000 people dead (possibly as many as 30,000), and traumatized millions of Mexicans who witnessed pancaked hospitals, collapsed homes and dead bodies strewn in the city’s rubble.  An early warning system was commissioned by Mexico City’s government consisting of 12 seismic sensors along the coast.  It was installed by 1991, and has since expanded to more than 100 sensors along the Mexican Pacific coast.  Government radio channels send out alerts and sirens after sensors detect menacing trembling, and residents can get about a minute or two of warning before the seismic waves arrive. 

Yet lessons learned by Mexico in reducing the catastrophic effects of an earthquake tragedy may not make it north of the border.  The US Geological Survey has spent years building a seismic early warning system on the West Coast.  It was due to launch in 2018, but US President Donald Trump’s budget would kill the program by canceling its $10 million in funding before it launches, reports the Los Angeles Times.  Congressional representatives from both parties are pushing back, and the system’s fate is still in limbo. 

The next earthquake is just a matter of time.  The USGS estimates California has a 99.7% chance of a magnitude 6.7 or larger earthquake, while the Pacific Northwest has a 10% chance of a catastrophic 8 to 9 magnitude earthquake, within the next 30 years.  The USGS says an early warning system along the Pacific coast of the US would alert residents anywhere from a few seconds (if the quake hits a population center) to much longer before a quake strikes a large area.  Both scenarios allow people to avert catastrophic damage and deaths: trains and planes can come to a stop, cars can be blocked from bridges and tunnels, dangerous industrial systems can be automatically shut down while people can seek cover. 

Video from Japan, one of the most earthquake-prone countries in the world, and which has also implemented a national warning system, shows the early warning a resident might see.  During a broadcast of one of Japan’s parliamentary hearings in 2011, an alert pops up (around the 30 second mark in the video) followed almost a minute later by the first shaking. 

This story was updated at 3:09am ET Sept. 20, 2017, with a revised toll and more information about the proposed US early warning system.