A Google official confirmed to HT that the company’s Android Earthquake Alerts System detected the initial seismic activity in Venezuela and sent warning notifications to users seconds before the earthquakes struck the South American country on Wednesday evening. The official did not specify how many users received the alerts.
The system, built into most Android phones, has been used to detect and warn of earthquakes in dozens of countries since 2020. A peer-reviewed assessment of its performance, funded by Google and published in the journal Science, has found that it can detect and warn of earthquakes at a scale comparable to established national seismic networks. Here’s how the system works:
How an earthquake is detected
Android relies on two detection methods. In California, Oregon and Washington, Google partnered with the US ShakeAlert system, which uses a network of 1,675 ground sensors to determine an earthquake’s location and size before passing a signal to Android.
Elsewhere, the system is crowdsourced. Every smartphone has a tiny accelerometer that can sense vibrations. When a phone picks up movement that could indicate an earthquake, it sends a signal, along with an approximate location, to Google’s detection server.
The server pools data from many phones to confirm whether an earthquake is underway, effectively turning millions of Android devices worldwide into a giant network of makeshift seismometers.
Also read: Venezuela earthquakes: Rescue ops enter ‘dangerous’ phase & why Caracas got caught in crosshairs
Two kinds of alerts
Both alert types are sent only for earthquakes of magnitude 4.5 or above. A ‘Be Aware’ alert is issued to users expected to feel weak or light shaking. This behaves like a regular notification and respects volume, ‘do not disturb’ and other notification settings.
But a ‘Take Action’ alert is reserved for users expected to feel moderate to extreme shaking. It overrides the smartphone settings, lights up the screen and plays a loud sound to grab attention. Tapping either alert brings up safety steps and a map with an early estimate of the earthquake’s location and magnitude.
Because alerts travel as electronic signals, they can reach phones before the slower-moving seismic waves arrive. Those few seconds, Google says, can be enough for someone to get off a ladder, move away from heavy objects, or drop, cover and hold on before the shaking begins.
Citing the example of Philippines, which was struck by a 6.7-magnitude earthquake in November 2023, Google says its system sent out the first alert just 18.3 seconds after the tremors started. People closest to the epicentre received up to 15 seconds of warning. Those farther away, who felt moderate shaking, got up to a minute of warning. In total, nearly 2.5 million people were alerted.
Also read: Two earthquakes, two epicentres, 39 seconds apart: The ‘doublet’ that shook Venezuela
Where, since when and efficacy
Google began the supplemental system in the US in 2020 through the ShakeAlert partnership. It started rolling out alerts based on its own crowdsourced detections in April 2021, beginning in New Zealand and Greece, and has since expanded the system to 98 countries, including India.
This system remains in addition to, and does not replace, official government warning systems.
A study on the alerts system, titled ‘Global earthquake detection and warning using Android phones’, was funded by Google and published in the journal Science on July 17, 2025.
Led by Richard M. Allen, with co-authors, including Google researchers, the study assessed three years of the system’s operation. It found that the system detected an average of 312 earthquakes a month worldwide, ranging from magnitude 1.9 to 7.8.
Alerts were delivered to 98 countries for roughly 60 earthquakes of magnitude 4.5 or above a month, reaching about 18 million phones in that period.
Among users surveyed who received an alert, 85% reported actually feeling the tremors. Of them, 36% got the alert before the tremors were felt, 28% during, and 23% after tremors had already started.
