Because seismic waves are slower than internet signals, it's possible to send an alert after an earthquake starts, but before the shaking reaches you. A few seconds' warning is enough to pull over to the side of the road, climb down from a ladder, step away from a high shelf or window, put down a scalpel, etc.
Mexico & Japan both have systems like this, and Los Angeles has launched a pilot program with apps for both Android and iOS.
The Wandering Shop is a Mastodon instance initially geared for the science fiction and fantasy community but open to anyone. We want our 'local' timeline to have the feel of a coffee shop at a good convention: tables full of friendly conversation on a wide variety of topics. We welcome everyone who wants to participate, so long as you're willing to abide by our code of conduct.