This research paper describes the Android Earthquake Alerts (AEA) system, a global earthquake early-warning (EEW) network that utilizes the accelerometers in consumer Android smartphones. By turning the vast, globally distributed network of phones into a seismic detection grid, the system provides warnings to regions that lack traditional, costly seismic stations. Over a three-year operational period, the system detected thousands of earthquakes, issuing alerts in 98 countries and expanding EEW access tenfold to 2.5 billion people. The system demonstrates magnitude estimation accuracy comparable to established government-run networks. Analysis of over 1.5 million user survey responses reveals that the alerts are overwhelmingly perceived as helpful, with 36% of recipients receiving the warning before shaking starts, demonstrating the viability and effectiveness of crowdsourced data for large-scale hazard mitigation.
Harnessing Smartphones for Global Earthquake Alerts: Key Findings
A Global Seismometer Network: The Android Earthquake Alerts (AEA) system uses the built-in accelerometers of stationary Android phones to detect P and S waves. When a phone triggers, it sends location and acceleration data to Google servers, which aggregate the information to rapidly detect an earthquake, estimate its parameters, and issue warnings.
Unprecedented Scale and Access: In three years, the system expanded EEW access from 250 million people to 2.5 billion across 98 countries. It detected an average of 312 earthquakes per month (magnitudes 1.9 to 7.8) and issued alerts for approximately 60 events per month (M ≥4.5).
High Accuracy Comparable to Traditional Systems: Despite using consumer sensors, AEA's magnitude estimation is highly accurate, with a median absolute error of 0.3. This performance is on par with, or slightly better than, established EEW systems like the US ShakeAlert and Japan's JMA, which rely on dedicated seismic stations.
Two-Tier Alert System: AEA delivers two types of alerts based on expected shaking intensity.
BeAware: A standard notification for light to moderate shaking (MMI 3 or 4).
TakeAction: A full-screen, loud, intrusive alert for strong shaking (MMI 5+) that is designed to prompt immediate protective action like "Drop, Cover, and Hold On."
Proven Real-World Performance and Warning Times: Case studies show the system's effectiveness. For a M 6.7 quake in the Philippines, users received up to 15 seconds of warning before severe shaking. For a M 5.7 quake in Nepal, over 10 million BeAware alerts were delivered, with many receiving 10-60 seconds of warning.
Learning and Improving from Major Earthquakes: Post-event analysis of the M 7.8 Türkiye earthquake revealed initial limitations and led to significant algorithm improvements. Simulations show the updated system would have provided up to a 35-second warning before the heaviest shaking, demonstrating a commitment to continuous enhancement.
Overwhelmingly Positive User Feedback: An analysis of over 1.5 million user survey responses shows that 85% of recipients found the alert "very helpful." This high rating holds even for the 79% of users who received an alert but did not feel shaking, highlighting the system's informational and educational value.
Driving Protective Action and Building Trust: The alerts are effective at prompting action. For high-urgency "TakeAction" alerts, the most common response was the recommended "Drop, Cover, and Hold On" (28% of recipients). A crucial 84% of survey respondents reported that their experience made them trust the system more in the future.