SAN FRANCISCO — Your phone can now warn you before an earthquake arrives.
This feat of science and personal technology is the best example I’ve seen of how smartphones can help protect tens of millions of us from significant danger. I’ll show you how to get it.
Known as ShakeAlert, America’s earthquake early-warning system was developed by the U.S. Geological Survey and partners to give you typically up to 20 seconds of advance warning before significant shaking arrives, or even a minute in extreme circumstances. If you’re close to the epicenter, you might not get much notice — but it could still be enough to protect yourself.
After nearly two decades of development, ShakeAlert is now operating in California, Oregon and Washington state, where it’s considered 83 percent complete. The USGS is considering expanding the system to Alaska next.
ShakeAlert got one of its largest tests with that October earthquake, when it took less than 10 seconds for the system to send about 2.1 million warnings to Californians like me. Thankfully, there were no reports of major injuries. For me, the little bit of early notice helped me prepare mentally for what was about to come.
The experience also left me wondering: How can a push alert reach my phone faster than shaking does? “That’s a multistage process, and really I find it just fascinating that we can do it all,” says Dave Croker, a member of the ShakeAlert operations team at the USGS.
I met up with Croker at a USGS field station a few miles from California’s notorious San Andreas Fault, where he showed me how the system fits together — starting with your cellphone.
How to get earthquake alerts on your phone
Smartphones have a capability that Croker says is a game changer for earthquake safety: They always know your location.
When a USGS field station detects an earthquake starting in one place, its network can calculate where else will likely also experience shaking. Knowing your location means the apps and cell towers can beam out the warnings only to the phones in places that might need it.
It’s easy to take smartphones for granted, but the last time San Francisco had a major earthquake — in 1989 — officials could communicate with people only over radio, TV and loudspeakers.
Today, the USGS doesn’t beam out ShakeAlerts to phones directly. Instead, it produces the information and then lets partner apps and cell carriers deliver the warnings. (There’s hope for the future that alerts could also go directly to internet-connected speakers and smoke alarms, and automatically instruct trains and elevators to slow or stop.)
If you have an Android phone, you’re good to go. Google added ShakeAlert to its operating system in 2020 after the California portion first came online. The warnings pop up automatically on your phone’s lock screen, so long as you have location services and emergency notifications enabled. These alerts are tuned to arrive for earthquakes that are both at least magnitude 4.5 and are also expected to produce noticeable shaking at your location. (If severe shaking is expected, Android will send a special take-action alert.)
If you use an iPhone, there’s a bit more work involved. You’ll need to download and run a free app such as MyShake, made by the University of California at Berkeley, or QuakeAlert. Unfortunately, you’ll have to repeatedly give the app permission to know your location at all times. (Apple, which has been heavily touting other iPhone safety features, said it didn’t have anything to share about integrating earthquake alerts into iOS.)
Regardless of what kind of phone you use, ShakeAlert can still find its way to you if an earthquake of magnitude 5 or higher hits. For areas also likely to surpass a high shaking threshold, wireless carriers are equipped to automatically send warnings to every phone using a similar emergency system to Amber Alerts. You just need to have government alerts activated in your phone’s settings.
Where earthquake warnings come from
So how do they figure out there’s an earthquake headed your way?
USGS’s Croker asked me to meet him on a little spit of land on the west side of the San Francisco Bay. There, he unlocked a green box bolted to the ground.
Inside are two motion sensors that don’t look anything like the seismographs I pictured with bouncing needles. One is a pro-grade version of an accelerometer (like we have in our phones) that can measure very violent shaking, and the other is a velocity sensor to detect very small trembles.
These sensors, powered by a nearby solar panel and battery, beam their readings back to the USGS central computers 24 hours per day. That connects them into a network of about 1,400 other sensor stations up and down the West Coast. In densely populated and known seismically active areas like the Bay Area, they’re located every 3 to 6 miles. But Croker says the system also needs geographical distribution to work. “The Earth never reveals all her secrets — we still have earthquakes in places we’re not sure they’re going to happen,” he says.
When the sensors report significant shaking, some serious math begins on the USGS computers. First they determine the magnitude and location of the quake — triangulating readings from multiple sensors to weed out false alarms.
Then they use these clues to estimate where else shaking will occur. “It took a lot of smart people to figure out how to turn the magnitude into an estimated ground shaking intensity level quickly enough that it could determine the area to which we send the alert,” Croker says.
It crunches the numbers in less than five seconds, and then the USGS’s partners beam the warnings across the internet and through cellular data signals at the speed of light.
The system is effective because long-range earthquake waves travel through rock relatively slowly — speeds can be as low as 1.9 miles per second. That’s why the farther you are from the epicenter, the more warning you’ll receive.
But you’re still going to need a plan for what to do when you see that alert. Forget the adage about going under a doorway, says Croker. Instead, emergency officials say you should drop and grab onto something solid like a wall, and cover your head to protect from any falling debris.
Your cellphone really could save your life — if you’re prepared.