In California, Washington, and Oregon, we partner with the ShakeAlert® team to distribute alerts provided by their system. ShakeAlert uses a network of 1675 seismic sensors to detect earthquake shaking, and analyzes that data to determine the location and size of the earthquake. The ShakeAlert® system then sends a signal to Android Earthquake Alerts System, which then sends an earthquake alert directly to Android users.
Outside of these U.S. states, we use a crowdsourced approach to detect earthquakes. All smartphones contain tiny accelerometers that can sense vibrations, which indicate that an earthquake may be happening. If the phone detects something that it thinks may be an earthquake, it sends a signal to our earthquake detection server, along with a coarse location of where the shaking occurred. The server then combines information from many phones to figure out if an earthquake is happening. This approach uses the 2+billion Android phones in use around the world as mini-seismometers to create the world’s largest earthquake detection network; the phones detect the vibration and speed of shaking of an earthquake, and alert Android users in affected areas accordingly.