Google sent quake alerts across Venezuela seconds before it struck. Here's how

Venezuela was struck by two of the most powerful earthquakes the country has faced in a century. But some users found that Google alerted them about the earthquakes before they happened. Here is how Google knew that an earthquake was coming.

In Short

• Google sent alerts to users before earthquake hit Venezuela
• Google uses Android phones as a large network of earthquake detectors
• Your phone can notify Google when it thinks there is an earthquake

On Wednesday, Venezuela was struck by two back–to-back earthquakes that led to the collapse of multiple buildings and widespread damage. The two earthquakes, measuring 7.1 and 7.5 in magnitude, are said to have been the most powerful to hit Venezuela in a century. But some users on X pointed out that Google already knew about an earthquake approaching, moments before they actually felt it.

On X, one user shared a screenshot of a notification from Google warning them of an earthquake. The earthquake alert flagged that an estimated magnitude 6.2 quake had been detected about 212.3 miles (roughly 341 km) away.

But how did Google know that an earthquake was coming? You see, the answer is related to your smartphone.

Google’s massive network to detect earthquakes

Every modern smartphone comes with an accelerometer. Usually, an accelerometer is the sensor that automatically rotates your screen when you hold it in landscape mode. But it has another use – it can detect and measure vibrations.

When your smartphone detects vibrations that may be strong enough to be that of an earthquake, it sends a signal to Google’s Android Earthquake Alerts System along with a rough location of where this happened.

Google’s servers then combine information from many phones to work out if an earthquake is happening. That is, after one smartphone sends such a signal, the server can then look at other phones in the area. If enough phones detect similar vibrations, Google knows that an earthquake is coming. And thus, it can send alerts.

And Google has over 2 billion Android phones that are part of this network. This makes it the largest distributed seismograph – earthquake detector – in the world.

Your phone is faster than an earthquake

But you may wonder, how is it that Google is able to notify you before you even feel the earthquake? To understand this, you first must know that an earthquake is not a single jolt. Rather, it happens in waves.

The Primary waves, or P-waves, are fast, and travel at roughly 6 km per second. But these are relatively weak when compared to the Secondary waves (S-waves) – travelling around 3-4 km per second – that do most of the damage.

This means that your phone can figure out that an earthquake is coming as it detects the P-waves, and quickly notifies the server. Since the signal from your phone travels at the speed of light, Google gets enough time to talk to other phones in the area and understand if an earthquake is actually coming.

Google says, “We’re essentially racing the speed of light (which is roughly the speed at which signals from a phone travel) against the speed of an earthquake. And lucky for us, the speed of light is much faster!”

For your reference, the speed of light is just over 299,792 km per second – much faster than the speed of earthquake waves.

This means that if the epicentre of an earthquake is 341 km away from where you are – as in the example for the Venezuela incident – Google’s servers will have received the signals, understood what was happening, and sent alerts, before the waves actually reached you.

Android has two types of earthquake alerts depending on the intensity of the earthquakes. The Be Aware Alert is meant to give users a heads-up for light shaking, while the Take Action Alert is designed to warn users before moderate to heavy shaking so that they can take steps to protect themselves. Tapping either alert shows earthquake safety information, including simple steps users can take to keep themselves safer after an earthquake. It also provides a detailed map with an early estimate of the earthquake’s location and magnitude.

The Android Earthquake Alerts System has been active in India since 2023 on phones running Android 5 and above. But to receive alerts, users must have Wi-Fi or cellular data connectivity. If you do not wish to receive such alerts, you can turn off Earthquake Alerts in device settings.

- Ends