We do have the same system, commonly used for Amber Alerts, Silver Alerts, Blue Alerts, fires, floods, COVID-19 lockdown, foreign missile tests, etc. However there's no mandatory ack, and except for "presidential alerts" they can all be turned off. That's what I did after I got woken up for an evacuation notice 20 miles away from me, feel back asleep, and got woken up again by the followup message 30 minutes later saying it was just a drill.
Anyways, the wireless emergency alert system has like 5-30s of latency. I suspect that might be enough to make push notifications a better solution. There's a # of apps taking that approach (full disclosure, my employer makes one of them), I think they all ingest data from a private USGS Kafka server
The WEA alerts use a pretty high threshold for whether or not to message people, and it's only been in place for a few years. It's possible you haven't been in an intense enough location during a 5+ magnitude earthquake. You might be interested in the ShakeAlert after action reports[1] which include maps showing roughly who was notified, how much advance warning someone potentially received, etc.
One downside with WEA is that it doesn't give a ton of granularity, so in theory they only issue them in areas where the alert will potentially save lives (despite latency concerns). One thing that the Android alerts do which I think is smart is to send out lower-priority alerts for non-dangerous earthquakes that still have enough intensity to be felt. Having that lower prio alert helps build confidence and trust in the system. Turns out people actually like advance warnings for smaller earthquakes, and unlike a real "oh shit duck and cover" alert those ones don't bypass Do Not Disturb mode.
I've always lived in Los Angeles and Bay Area until a month ago. But the one "duck and cover" earthquake here in the 21st century was probably before these alerts existed.
Anyways, the wireless emergency alert system has like 5-30s of latency. I suspect that might be enough to make push notifications a better solution. There's a # of apps taking that approach (full disclosure, my employer makes one of them), I think they all ingest data from a private USGS Kafka server