Last year, Google a new earthquake alert system for Android. At the time, it was California-only and based on the USGS's ShakeAlert, but the company also started work on another plan: Using the world's army of Android phones themselves to gather seismological data for earlier detection, notifications, and better accuracy. At the time, that crowdsourced data was limited to Google Search, but today Google is bringing it in the form of early earthquake detection notifications to phones, too — but only if you live in New Zealand or Greece.
Above: Earthquake alerts (for the ShakeAlert system). Below: Crowdsourcing after-the-fact earthquake data in Search.
Crowdsourcing earthquake detection is honestly a really great idea. After all, Android phones are everywhere, and they're loaded with sensors like accelerometers that can pick up on those earth-shaking motions in places that scientists and government agencies might not have fixed seismometers. Though I'm sure the quality of individual sensor data may not be as good, that's likely compensated for by the sheer number of devices and their wider and more granular coverage.
The precise lineage of this feature's rollout is a little complicated since Google's been gathering seismological data from Android phones since last year (shortly after it announced the California alerts), but our understanding of the general timeline is as follows. First, Google integrated with the ShakeAlert system for those California warnings on Android phones, harnessing 700 existing seismographs in the state. But even as it rolled that feature out, it had already started crowdsourcing data from Android device accelerometers.
That use of device sensors to gather data landed in Google Search as after-the-fact mapping for earthquakes, helping better estimate severity and the epicenter of events after they occurred. Later, Google rolled out the ShakeAlert-based system to Oregon, and it's coming to Washington next month as well, but today's announcement is the first time (to our knowledge) that Google's separate crowdsourced data has been used for these new early on-phone alerts. (Presumably, after looking at the data gathered over the last half-year or so, Google's scientists found the crowdsourced system was sensitive enough to pick up on early indicators of an earthquake.)
Google is rolling out the new crowdsourced alert system first to Greece and New Zealand, claiming it's altruistically doing it first for countries that don't have their own early warning systems. We don't have precise timing for the feature or the mechanism for its rollout, but based on the details of Google's announcement, it should be landing in both countries quite soon. And if you don't want the alerts for some reason, it's easy to turn them off in Settings.