credit, Getty Images
- author, Tom Ogg
- roll, BBC Future
On October 25, 2022, a 5.1 magnitude earthquake struck the Bay Area of California in the United States.
Fortunately, it was more of a tremor than a violent quake. But a lot of information from residents in the affected area reached the USGS.
No damage was reported, but the quake was big for another reason. Many people in the area received alerts on their cell phones before the tremors began.
Similar warnings about a 5.2-magnitude earthquake centered south of Bakersfield reached Southern California residents as early as 30 seconds into the night of Aug. 6, 2024.
More importantly, many of these phones also helped detect an earthquake before it happened.
Google is working with the US Geological Survey and academics from several California universities to develop an early warning system that would warn users just seconds before tremors hit.
The warning window is short, but even a few seconds can provide enough time for people to seek shelter under a table or counter. It can also be enough to slow trains, prevent planes from taking off or landing, and prevent cars from entering bridges or tunnels.
With this, the system can save lives in the event of more powerful earthquakes.
The data comes from two sources. Initially, the system included a network of 700 seismometers—devices that detect earthquakes—installed across the state by seismologists from the U.S. Geological Survey, the California Institute of Technology, the University of California, Berkeley, and the state government.
Seismometers installed in two other US states — Oregon and Washington — also send data to the system, known as ShakeAlert. But Google is working to create the world’s largest earthquake detection network from users’ mobile phones.
Most Android smartphones have built-in accelerometers — circuits that detect the movements of the cell phone.
These circles are often used to direct the phone to reorient its screen between portrait and landscape when the device is tilted, for example. They also help provide step count information to Google's built-in fitness tracker.
But the sensors are surprisingly sensitive, and can also serve as mini seismometers.
Google has introduced a feature that allows users to have their devices automatically send data to the Android earthquake alert system when they detect the characteristic vibrations of primary (P) earthquake waves.
By combining data from thousands or even millions of other cell phones, the system can infer whether and where an earthquake is occurring. It can then send alerts to phones in the area likely to be hit by seismic waves, providing early warning.
Because radio signals travel faster than seismic waves, warnings can arrive before earthquakes begin, in areas far from the epicenter.
Android software engineer Mark Stogaitis defines the system as follows:
“Basically, we are racing at the speed of light (the approximate speed at which phone signals travel) against the speed of the earthquake. Luckily for us, the speed of light is much faster!”
Because most of the data is collected collaboratively, the technology opens up the possibility of monitoring earthquakes in areas where there are no large-scale networks of expensive seismometers. In other words, it increases the possibility of providing earthquake warnings even in the poorest, most remote areas of the planet.
In October 2022, Google engineers saw cellphones across the San Francisco Bay Area light up with earthquake detection data as seismic waves traveled away from the epicenter.
Now, the system regularly picks up these tremors so that the USGS’s ShakeAlert program can issue alerts when they exceed certain thresholds, sending messages to cell phones of users in areas likely to be hit by a quake.
While alerts can be received on Android phones, people in California, Oregon and Washington can also use the MyShake app, developed by researchers at the University of California, Berkeley. It turns users’ phones into earthquake detectors when they’re stationary and sends alerts based on the device’s location.
Earthquakes occur frequently in California. The state experiences up to 10 small earthquakes every day. Most of the time, they are too weak for people to feel.
But several larger earthquakes typically occur in California each year. There are about 15 to 20 quakes with a magnitude greater than 4.0.
Globally, it is estimated that there are 16 billion mobile phones in use worldwide, and more than three billion of them use the Android operating system. The earthquake warning system is now available in more than 90 countries that are particularly prone to earthquakes.
But the system also has its limitations, especially in remote areas, where there are few mobile phone users, and in earthquakes at sea, which can generate tsunamis.
Although these systems can issue warnings seconds in advance, predicting earthquakes before they occur remains a distant goal.
How to activate earthquake alerts on your cell phone
Settings for enabling earthquake alerts on Android phones can be found in the Security & Emergency section of your phone's Settings app. The system requires access to the Internet via Wi-Fi or mobile data.
iPhone owners in Japan can also enable emergency alerts in the Notifications section of their device's settings.
