seismograph

On June 24, a pair of earthquakes of magnitude 7.2 and 7.5 They shook northern Venezuela just 39 seconds apart, causing the largest seismic disaster the country has experienced in more than a century. The fatalities They already exceed 200with more than 4,300 injured and thousands missing. Collapsed buildings in Caracas, the international airport closed and an area of ​​devastation that extends for 150 kilometers. Curiously, seconds before the first earthquake hit, thousands of Android users in Venezuela received a notification on their phones. It is not that Google has the power to predict earthquakes, but the technical and scientific basis behind your alert system It’s fascinating. A country without an official seismic warning system. Venezuela does not have any national earthquake early warning system. If we compare with regions like Chile or Japan, which have thousands of seismic stations, the national network in Venezuela has less than 40and this is a huge limitation in terms of alerting and risk mapping capacity. The case of Venezuela was dramatic precisely due to this lack, since the country did not have enough time to evacuate. However, some people received warnings seconds or even minutes before noticing the tremor thanks to Google’s Android Earthquake Alerts system. Pericles Sánchez, a 39-year-old writer from Caracas, He received the alert on his mobile phone with enough time to get out onto the street before the strongest shock came. As he explained, his family did not suffer damage to the house. How Google turns cell phones into seismographs. All smartphones have tiny accelerometers that can detect signs indicative of a possible earthquake. If your phone detects something that could be an earthquake, it sends a signal to Google’s detection server along with your approximate location. That server combines information from many phones to determine if an earthquake is really occurring. This is how Google competes against time, as it takes advantage of the fact that digital signals travel at a speed well above the speed at which seismic waves propagate through the ground. The system also uses artificial intelligence models trained with thousands of documented seismic events to analyze the pattern, frequency and coherence of signals received from multiple devices simultaneously. The alert is only activated when a minimum number of telephones in the same area simultaneously confirm a recognizable seismic pattern. Physics. Earthquakes generate different types of waves that travel at different speeds. Primary, or P, waves move fast (about six kilometers per second) but cause little damage. Secondary, or S, waves are slower (about three to four kilometers per second) but are responsible for most of the destruction. The Android system detects the first P wavesthose that arrive first, and sends the warning signal before the Ss reach people. This margin can be a few seconds or, for those who are further away from the epicenter, up to a minute. During a magnitude 6.7 earthquake in the Philippines in November 2023, the system launched the first alert 18.3 seconds after the start of the earthquake. People closest to the epicenter received up to 15 seconds of warning and nearly 2.5 million people were alerted. Two types of alert, depending on the danger. The system emits two categories of notices for earthquakes of magnitude 4.5 or greater. The BeAware alert is designed for mild shocks and informs the user with a conventional notification that respects the phone’s silent mode. The TakeAction alert is reserved for more dangerous situations, taking control of the screen and emitting a loud sound even if the mobile is silent. In both there is information about the estimated magnitude, the distance to the epicenter and basic safety recommendations. A network of 2.5 billion people. Google has taken advantage of motion sensors more than 2 billion smartphones to create an earthquake early warning system that is as effective as conventional seismometers, according to a study published in the journal Science in July 2025. The system has detected more than 18,000 earthquakes since its deployment in April 2021 and currently operates in 98 countries. In the US it operates better than in the rest of the countries. The system does not operate the same everywhere. In California, Washington and Oregon, Google work with the ShakeAlert teamwhich uses a network of more than 1,600 seismic sensors installed in the ground to detect earthquakes and determine their location and magnitude before sending the data to Android devices. Outside of those states, the approach is what has been seen in Venezuela: collective detection using the accelerometers of millions of mobile phones, without physical infrastructure on the ground. And it is precisely in this second modality where the system is most valuable, because it covers regions of the world that have never been able to afford professional seismic networks. Cover image | Ricardo Aguilar and USGS In Xataka | “The biggest mistake of all time”: Bill Gates let slip 400 billion when Microsoft didn’t buy Android