We’ve all heard the sudden, shrill shriek of an Amber Alert blaring from our phones. It’s enough to jolt us out of a deep sleep, make us spill coffee all over our desk or jump a mile if we’re walking with our phone in our pocket. But now those attention-grabbing wireless emergency alerts are tackling one of the most challenging types of disasters to protect against: earthquakes.

Enter ShakeAlert, an earthquake early warning system that the U.S. Geological Survey and several university partners are rolling out. It can’t predict earthquakes. But it can frequently offer a few seconds warning before damaging earthquake waves arrive at a given location. And in a situation where fractions of a second count, it’s an important undertaking that’s already having results.

ShakeAlert is a USGS app for your phone. But USGS also feeds the data to Federal Emergency Management Agency, which disseminates applicable alerts through the U.S. Emergency Alert System on mobile devices.

On Jan. 22 at 7:03 p.m., the ground started to shake in Barstow, Calif., a city of nearly 24,000 in the Mojave Desert. Seconds later, an alert blasted to phones “downwind” of the quake warned of imminent or occurring tremors.

“Earthquake!” read the alert. “Expect shaking. Drop. Cover. Hold on.”

It’s unclear exactly how many people received the wireless emergency alert or whether they got it before the shaking began. But scientists feel this is a major leap in the right direction.

The technology

ShakeAlert, like earthquake early warning systems in other seismically active countries, relies on a dense network of seismometers to detect an earthquake almost immediately after it occurs. It usually takes a few seconds for the first signals of an earthquake deep in the ground to reach seismometers on the surface.

Once the first signal is received at several sensors, it’s transmitted to a data center where ultra-high-speed computer processors, replete with built-in ground motion algorithms, can attempt to pinpoint the location and magnitude of the quake. Initial estimates are often imperfect, but they provide a critical ballpark guess needed to jump-start the warning process.

From there, a digital map of just how bad the shaking will be is created. The jolt you feel is measured by the Modified Mercalli Intensity Scale (MMI). Intensity is different from earthquake magnitude, the latter a figure for how much energy is released when a fault slips.

The USGS ShakeAlert system then churns out automatic warnings to people expected to experience shaking above a certain magnitude. While the warning may come too late for those residing close to the quake’s epicenter, the ShakeAlert system can sometimes provide tens of seconds of warning before violent shaking arrives elsewhere.

That’s because the earthquakes less-damaging P waves, or compressional waves, move at about 3.5 miles per second. The speed of light is about 67 million mph. Radio signals move at the speed of light, so it’s possible for earthquake warnings to “outrun” the damaging S waves and surface waves that come thereafter. The tough part is rapidly getting the warning out.

How it’s being done

That’s where Robert Michael de Groot and his team come in. He’s the national coordinator for communication, education and outreach at ShakeAlert and a seismologist at USGS.

He said that the Jan. 22 wireless emergency alert that went out in Barstow was the first of its kind.

That quake was classified as a moment magnitude 4.6. That’s not enough to trigger a wireless emergency alert, but one went out anyway. Why?

“The system for [wireless emergency alerts] would only distribute at a 5.0 or above,” de Groot explained. “When we got the data from the field, [the system] estimated the earthquake at a 5.1.”

From the time USGS receives indication of an ongoing earthquake to the time it hits your phone is “on the order of 13 seconds,” according to de Groot.

“We’ve done two tests. We did a test in March of 2019 and in Oakland in June 2019,” he said. Some phones may process the alert even more quickly.

“In the case of the March and June tests, those were contrived,” de Groot said. “In this situation it’s a real event where the system did everything automatically. Our estimation at this point is ... 16 seconds to the first phone.”

Who can get these alerts?

Right now, California, Oregon, and Washington are wired to receive these alerts. Unsurprisingly, they’re the priority, as the West Coast is about as seismically active as it is densely populated.

Down the road, de Groot and his team hope to expand to other higher-risk areas in the United States.

“That’s 50 million people in three states,” de Groot said. “We want to finish.” But Alaska — the nation’s leader in earthquakes — may be next.

Alaskans are no stranger to earthquakes. A magnitude 7.1 struck Anchorage just before 8:30 a.m. on Nov. 30, 2018. Despite the massive shaking, damage was minimal and recovery swift: Public bus service in the state’s largest city resumed just two days later.

In California, wireless emergency alerts will only be sent out for quakes with estimated magnitudes greater than a 5. The ShakeAlert app activates for quakes at the 4.5 level — the threshold lowered when residents in Los Angeles complained after not receiving notice prior to some lighter shaking from the distant Ridgecrest quake last July.

“There was a lot of outcry,” de Groot said. “My skin grew a little thicker that day.”

De Groot notes that the public wants to be aware and “know what’s going on” during any earthquake. But he fears pushing out alerts for even nuisance quakes would cause desensitization. This is why wireless emergency alerts will be reserved for the big ones.

“We want people to take protective action when they receive [an alert].”

What should you do if you get an alert?

If you find yourself warned of an imminent earthquake, you only have seconds to act. Those close to the epicenter won’t have any warning at all.

“If you do get the ShakeAlert, take action,” said de Groot. But if an earthquake strikes without advanced notice, “still do what you would normally do. Don’t rely on warning.”

When an earthquake strikes, the most urgent threat comes from falling objects. Duck, cover and, if possible, seek refuge beneath a heavy, sturdy piece of furniture, such as a desk or table. Stay away from objects that could topple or shatter.

Even the brief amount of time spent glancing down and mentally processing the warning could cost valuable seconds. That’s why USGS is working with FEMA so that earthquake alerts can be accompanied by their own specific tone.

“We’re working to develop a tone so it provides that cognitive shortcut,” de Groot said. “[People will] say, ‘I know it’s an earthquake-based message and I need to take my precautions.’”

De Groot’s team have consulted emergency managers and social scientists in developing such a tone. Initially they had hoped to use the same “bling, bling, bling” cadence used in Japan and Chile, but the focus has since shifted to creating a U.S.-specific tone.

“We’re working with a sound engineer now.”

Why the U.S. is such a tough place to set up a system

Other earthquake-prone nations have developed similar systems for earthquake detection and early warning; some have been in use for more than a decade.

In Japan, an alert box pops up automatically on television, with two iterations of a designated tone followed by “this is an earthquake early warning.” Newscasters immediately switch into earthquake mode, relaying vital information on intensity and additional threats. If a tsunami alert is issued, that follows.

Some televisions are even equipped with the technology to turn on automatically and tune to NHK News, Japan’s public news channel.

Mexico’s seismic alert system, or SASMEX, relies on a similar network of sensors. Processing and dissemination of alerts in Mexico is also faster than in the U.S., with the alerts broadcast less than two seconds after preliminary data arrives. The system can provide close to a minute of advanced notice in Mexico City for some earthquakes thanks to the city’s distance from a dangerous subduction zone running just west of the Mexican state of Guerrero. Chile has a similar system too.

But in the United States, getting that much warning will be tough.

Technology gaps do play a role. “With most of our distribution systems, [the United States is] not built for speed,” de Groot said. “We had no idea when these [public alert] systems were being designed and built that we would be doing this. Latency is a challenge.”

But the geology of the region proves equally toilsome.

“You know Japan and Mexico, both countries have subduction zones that are pretty far off the coast. [The Mexican system] was designed ... with protecting Mexico City in mind."

But for the Pacific coast, the dangerous boundary doesn’t lurk offshore. It runs right through the heart of some of the most heavily populated land in America.

“The challenge with California, Washington, Oregon ... we have a lot of faults on land, so if you’re right on top of the fault, you’re sitting right on top of the source of the earthquake.”

When that happens, you’re not going to get an alert before the shaking. Only folks farther away from the epicenter will.