A new earthquake warning system at Cal Tech detected two 4.5-magnitude earthquakes near Yorba Linda, California on August 7 and 8. It was the first time any device detected quakes before they hit. Sound great, right? Who wouldn’t want a service like that? But the warning system detected the first quake a mere nine seconds before the ground shook. The second warning came four seconds before the quake. Even though this breakthrough shows that earthquakes can be detected before they happen, nine seconds isn’t much of a heads up. That isn’t enough time for anyone to prepare. Maybe this prototype earthquake detection technology will lead to systems that predict quakes in enough time to make a difference. In the meantime, make sure you’re prepared if you live in an earthquake-prone area. Learn more about earthquake preparedness at beprepared.com.
I think you're overlooking the advantage here: an earthquake warning would travel at the speed of light to alarms & sirens. It could give a family a few precious seconds to get moving before the first tremor is felt. Instead of being reactionary, you can be proactive.
Utilities could use this information to switch to "earthquake mode" on their equipment.
It's not much, but it's more than what people have now.