Your mobile device might already be part of the billions of gadgets worldwide functioning as an early warning system for earthquakes across numerous nations.

Launched in 2020, Google’s Android Earthquake Alerts System has expanded to reach 2.3 billion Android phone and smartwatch users, enabling them to receive alerts about seismic activity, according to a recent study by Google researchers. However, these devices do more than just issue warnings; they also contribute to earthquake detection.

“Billions of Android devices come together to form mini-seismometers, establishing the world’s largest earthquake detection network,” states Richard Allen, a visiting researcher at the University of California, Berkeley.

Developed by Allen and his team, the system analyzes vibrations captured by accelerometers in Android devices and smartwatches. This collective network of sensors can determine the magnitude of an earthquake and identify which users are in close range of danger for timely warning messages.

Google’s system alerts users when it detects tremors of 4.5 or greater on the Richter scale. Yet, Allen notes that the system “may not detect all earthquakes” due to the need for sufficient nearby devices. For instance, earthquakes from most central ridges may go undetected, but the system can identify seismic events occurring up to hundreds of kilometers offshore.

A critical challenge is the swift and accurate assessment of each earthquake’s magnitude. Researchers have refined the detection algorithm over time by creating regional models that better represent local structural movements and by considering the varying sensitivities of different Android devices.

According to Allen, Google’s global system is now as effective as the ShakeAlert system, which serves the US West Coast, as well as Japan’s early warning system. He emphasizes that Google’s initiative is intended to complement, not replace, seismometer-based services, which provide warnings like ShakeAlert to West Coast residents. “Many earthquake-prone areas lack the local seismic network necessary for timely alerts,” Allen comments.

Google’s system serves as a “unique source” for nations without an existing earthquake early warning framework, states Katsu Goda from Western University in Canada, who is not affiliated with the project. He noted that even in regions with existing alert systems, Google’s solution reaches a broader audience.

The system currently delivers alerts to 98 countries and territories, including the United States, but excluding the UK. “Our focus has primarily been on countries at high historical risk for earthquakes that lack existing early warning solutions,” explains Marc Stogaitis from Google.

A recent study evaluating system performance and accuracy revealed that the system generated alerts for 1,279 earthquake events up until March 2024, with only three false alarms. Of these, two were due to thunderstorms and one stemmed from an unrelated mass notification that caused several phones to vibrate. The research team improved their detection algorithm to minimize these types of false alerts.

Most Android devices are automatically enrolled in a mobile phone-based seismometer network and receive alerts regarding nearby earthquakes by default, although users can modify these settings. In a Google User Survey, over one-third of participants reported receiving alerts before feeling any shaking, and most indicated that these notifications were extremely beneficial.

If users remain subscribed to alerts, they will receive two types of notifications: more urgent action alerts encouraging immediate precautions like “drop, cover, hold,” which often provide only a few seconds of advance warning, and out-of-interference alerts that share general information, allowing a brief window before a user experiences the earthquake.

“The nature of earthquakes implies that there are less warning time before strong shaking compared to weaker events,” states Stogaitis. “Nonetheless, we are continuously examining adjustments to our alert strategies to extend warning times for future earthquakes.”