Friday’s magnitude 7.2 earthquake in the Mexican state of Oaxaca was another opportunity to demonstrate the benefits of an earthquake early-warning system, which in some seismic events, can send an alert ahead to cities before damaging waves can reach them. That means that in a place like Mexico City, which is built atop the weak soils of a former lakebed, people there had an approximately 1-minute warning to move outdoors and away from buildings or take shelter in a sturdy location before the shaking started.

Fortunately for Mexico City, the impacts from Friday’s quake were minimal compared to more damaging earthquakes in September with epicenters closer to the capital, killing several hundred people there and surrounding states.

While places like Japan and Mexico have deployed earthquake early-warning systems, the U.S. has been sluggish in developing one for quake-prone areas along the West Coast.

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