Google alerted users seconds before Venezuela's earthquake. Here's how Android phones detect tremors

Two powerful earthquakes that struck Venezuela on Wednesday evening have drawn attention not only for the widespread destruction they caused but also for the early warnings received by several Android users before the tremors were felt.

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.

The answer lies in Google's Android Earthquake Alerts System, which turns millions of smartphones into a vast earthquake detection network.

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.

Android users received earthquake alerts moments before powerful tremors

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.

With more than two billion Android devices worldwide, Google says it has built the world's largest distributed earthquake detection network.

The reason these alerts often arrive before people feel the earthquake is because earthquakes travel in different types of waves.

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.

As Android phones detect the faster P-waves, they immediately transmit the information to Google's servers. Since data travels at nearly the speed of light, Google's systems can analyse reports from multiple devices and issue alerts before the slower, stronger S-waves reach users.

Explaining the technology, 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!"

Google's Earthquake Alerts System uses billions of smartphones to identify seismic activity and issue early warnings

Android offers two types of earthquake notifications. The Be Aware Alert is issued for light shaking, while the Take Action Alert warns users before moderate to heavy shaking and includes safety guidance along with an estimated earthquake location and magnitude.

The Android Earthquake Alerts System has been available in India since 2023 on devices running Android 5 and above. To receive alerts, users must have Wi-Fi or mobile data enabled. Those who do not wish to receive them can disable Earthquake Alerts through their device settings.

According to the US Geological Survey (USGS), a magnitude 7.2 earthquake struck near Montalbán, west of the coastal town of Morón, at 18:04 local time. Minutes later, a stronger magnitude 7.5 earthquake hit the same region. The USGS warned that the twin quakes could cause widespread devastation.

"High casualties and extensive damage are probable and the disaster is likely widespread," the agency said, initially estimating that the death toll could range between 10,000 and 100,000.

According to Reuters, authorities had not immediately released official casualty figures. The tremors were felt across Venezuela and neighbouring Colombia.

Venezuela's Interior Minister Diosdado Cabello confirmed that several buildings had been damaged in Caracas, PTI reported. He urged residents to remain outdoors because of possible aftershocks.

"We understand that some people may be desperate, but we are acting according to protocols to activate aid and rescue efforts to help those who need it most," Cabello said. "Be very careful with children and the elderly; call each other and check that no one has been harmed."

Following the earthquakes, tsunami threats and advisories were issued for several Caribbean regions as emergency teams continued rescue and relief operations.