Many social media users in Venezuela have reported receiving alerts on Android smartphones moments before Wednesday’s quake that left over 900 confirmed dead.

Google’s Android and Apple’s iOS both include the option to display government alerts for emergencies like earthquakes.

But the search giant last year also detailed its system that uses the billions of Android smartphones worldwide to detect earthquakes in the first place.

How it works

Almost all smartphones contain an accelerometer, a movement sensor used for tasks like flipping the screen when users turn it sideways.

That same sensor “can also detect the ground shaking from an earthquake,” Google wrote in a July 2025 blog post.

Accelerometers can spot potential earthquakes’ fast-moving initial “P” wave, sending information about the tremor to a Google server.

By rapidly cross-referencing many such reports, the system can “confirm that an earthquake is happening and estimate its location and magnitude,” Google said.

“The goal is to warn as many people as possible before the slower, more damaging S-wave of an earthquake reaches them”.

Google offers two stages of alerts.

“BeAware” warns of weaker tremors, while for the heaviest quakes, “TakeAction” takes over the screen and plays a loud sound even when the phone is on silent mode.

How effective is the system?

Google said last year that its systems had already sent 790 million alerts to individual phones, warning of over 2,000 potentially dangerous earthquakes detected from April 2021.

While that gives many more people than before access to early warning information, there have been hiccups.

Android phones failed to sound warnings ahead of devastating February 2023 earthquakes that killed almost 60,000 people across Turkey and Syria.

Google said last year that it has since updated its algorithms to avoid a repeat.

The company also apologised in February 2025 for a false alarm sent to some Android users in Brazil.

This week in Venezuela, hundreds of people have posted praise for Google on X, with some including unverified videos of alerts prompting people to leave buildings.

What about Apple?

Beyond government warnings, Apple says on its website that users in the US and Taiwan can also receive alerts from other “alert originators” about earthquakes.

The company did not respond to AFP’s questions about how that system works by time of publication.

Neither has the iPhone giant enlisted its users’ phones for a distributed detection system like Google’s.

The hundreds of millions of iPhones around the globe are, however, able to forward alerts they receive to other nearby Apple devices that do not have mobile reception or a WiFi connection — potentially helping life-saving warnings to get through.