When the two big ones — a magnitude 7.2 followed 39 seconds later by a stronger 7.5 — jolted the , some were quick to report on social media that their phones “rang” before they even felt the tremor.
The first earthquake occurred at 6:04 p.m. (US East Coast time), while the second, stronger, mainshock followed about 39 seconds later. Footage was released on X and elsewhere showing alerts detecting the quake from about 341 kilometers away, seconds before the quake was felt.
🇻🇪 The Google Alert seconds before the earthquake managed to save many lives. Here is an example of it.
— Venezuela News (@AgenciaVNews)
Of course, this has given rise to various scenarios with many wondering how it is possible that Google knew an earthquake was going to happen before it happened, or how it is possible that Google predicted the earthquake. These questions started mixing with conspiracy theories and things went their way online.
The “science” behind the difference between prediction and detection
But in practice, many citizens seem to have managed to use the time until the real “wave” of the earthquake arrived and move to a safer place because of these alerts.
That is why it is of interest to better understand how Google’s notification system works. According to experts, when an earthquake starts, two types of waves are released. Faster but less destructive primary waves (P-waves) arrive first. The slower secondary waves (S-waves) and surface waves — the ones that cause the real damage to buildings and networks — arrive a few to many seconds later, depending on the distance from the epicenter.
Internet and cell phone signals, which travel at nearly the speed of light, can “catch up” on these slow seismic waves. So when Google’s system detects the start of an earthquake near the epicenter, it has a short “window” — a few seconds to almost a minute for more distant areas — to send a warning before the strong tremor arrives. This is not a prediction, but an early detection.
Google detects earthquakes in time using the mobile phone as a seismograph
In the case of Venezuela, the country does not have a traditional state earthquake early warning network, like the one that exists in parts of the US. Outside of such systems, Google uses a “massive” approach: modern smartphones have tiny acceleration sensors (accelerometers) that can register vibrations.
In practice, any Android phone with this feature enabled works like a simple seismograph. When the mobile detects an earthquake-like vibration, it sends a signal to Google servers along with the approximate location. The system combines data from thousands of cellphones to confirm if it is indeed an earthquake.
In this way, more than two billion Android devices worldwide become — according to Google — the largest earthquake detection network in the world.
Once enough signals are gathered, the system estimates the magnitude of the earthquake and sends two-level alerts: a milder “Be Aware” for light tremors and an urgent “Take Action” for strong tremors that require immediate protection. That was likely the kind of notice residents in Venezuela received.
