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Two powerful earthquakes<\/a> that struck Venezuela<\/a> on Wednesday evening have drawn attention not only for the widespread destruction they caused but also for the early warnings received by several Android<\/a> users before the tremors were felt.<\/p>\n<\/div>\n Social media users shared screenshots of Google notifications warning them of an approaching earthquake. One alert estimated a magnitude 6.2 quake about 212.3 miles (roughly 341 km) away, prompting many to ask how Google was able to send alerts before the ground started shaking.<\/p>\n<\/div>\n The answer lies in Google’s Android Earthquake Alerts System, which turns millions of smartphones into a vast earthquake detection network.<\/p>\n<\/div>\n Every modern Android smartphone is equipped with an accelerometer, a sensor commonly used to rotate the screen automatically. The same sensor can also detect ground vibrations associated with an earthquake.<\/p>\n<\/div>\n When a phone detects vibrations that resemble seismic activity, it anonymously sends a signal along with an approximate location to Google’s servers. The system then compares information from multiple nearby Android devices. If enough phones detect similar vibrations at the same time, Google determines that an earthquake may be underway and sends alerts to users in affected areas.<\/p>\n<\/div>\n With more than two billion Android devices worldwide, Google says it has built the world’s largest distributed earthquake detection network.<\/p>\n<\/div>\n The reason these alerts often arrive before people feel the earthquake is because earthquakes travel in different types of waves.<\/p>\n<\/div>\n Primary waves, known as P-waves, travel at roughly 6 km per second and are generally weaker. Secondary waves, or S-waves, move more slowly at around 3 to 4 km per second but cause most of the damaging shaking.<\/p>\n<\/div>\nAndroid users received earthquake alerts moments before powerful tremors<\/h2>\n