On Tuesday, officials in Washington state flipped the switch that enables earthquake early warnings to be disseminated to residents of the state. Washington joins California and Oregon, where such warnings are already enabled, in making “ShakeAlert,” a high-tech warning system that can provide notice seconds before the ground starts shaking, a reality for more than 50 million Americans.

The system will now alert residents of imminent shaking from a magnitude 5.0 or greater quake, providing up to tens of seconds of notice before the shaking starts. They will activate cellphones via wireless emergency alerts, similar to Amber Alerts or severe weather warnings. It’s a key step in preparing for a major earthquake, like the one scientists fear will someday strike off the coast of Washington state, spelling disaster.

ShakeAlert follows in the footsteps of other earthquake-prone nations such as Japan, Mexico and Chile, where earthquake early warnings are often broadcast live on television up to a minute before residents experience shaking.

How the system works

The system doesn’t predict earthquakes — that’s impossible. While seismologists and geologists can designate a probability of a given fault slipping, science doesn’t allow for more specific predictions.

ShakeAlert is composed of a dense network of seismometers scattered about California and the Pacific Northwest. When the initial “body waves” of an earthquake are detected, sensors quickly beam information to the University of Washington, where ultrarapid computers determine the approximate depth, magnitude and location of the shaking. Body waves travel through the Earth and are seldom damaging — but they contain vital information about a quake.

If the computer algorithms deduce that the earthquake is large enough to pose a substantial threat, it automatically beams earthquake early warnings to communities in line for shaking. Since the messages are transmitted at the speed of light — about 180,000 miles per second — they can often beat the damaging surface waves of an earthquake, which roll along at only a few miles per second.

Where the message will go

The farther you are from the epicenter, the more advanced notice you’ll receive. ShakeAlert won’t help those in the immediate vicinity of the quake, who will be jarred immediately.

“Seconds can save lives and reduce injuries by giving people time to take protective action,” David Applegate, acting director of the U.S. Geological Survey, said in a news conference Tuesday. “It can trigger automated measures, too.”

Those automatic actions can be crucial for protecting vital infrastructure, including in utilities and transportation systems. In San Francisco, receipt of a ShakeAlert will automatically slow BART trains across the Bay Area.

“Imagine a surgeon holding a scalpel in the midst of surgery, a family at the beach, or a driver on Highway 16 about to cross the Tacoma-Narrows bridge,” Rep. Derek Kilmer (D), who serves Washington’s 6th Congressional District, which includes the Olympic Peninsula, said at the news conference.

Once an earthquake commences, cellphones may start squealing downstream in as little as 10 seconds.

“We know the system works,” Harold J. Tobin, director of the Pacific Northwest Seismic Network at the University of Washington, said at the news conference.

“A number of alerts have gone out in California. In September 2020, a quake of magnitude 4.5 occurred in the L.A. city region,” he said. “The earthquake was not large enough for a wireless emergency alert, since the limit is magnitude 5.0, but Android did deliver an alert to 2.2 million cellphones with an average time of 4.7 seconds since alert was generated, which was just a couple seconds after the earthquake began.”

Investing in preparation

The Federal Emergency Management Agency estimates that earthquakes cause an average loss of $5 billion annually, but ShakeAlert will cost only $28.6 million to maintain in 2022. That’s money being proposed by Rep. Suzan DelBene (D), congresswoman for Washington’s 1st Congressional District. She says it’s worth every penny.

“The prospect of a really devastating quake is a when not if scenario,” she said at the news conference.

“Federal and state investments … make the whole system more robust,” agreed Applegate.

ShakeAlert was born out of a partnership between the U.S. Geological Survey and half a dozen universities on the West Coast. While the servers that process sensor data are regionally based, researchers at the University of Oregon, the University of California at Berkeley, the California Institute of Technology and the University of Nevada at Reno played a role.

“If there’s any place in the world that will hook you as a geologist, it’s the Olympic Peninsula,” said Applegate. That’s where ShakeAlert has the significant value if — and when — the “Big One” strikes.

Applegate referred to the “Big One,” to an eventual quake that could occur when the Cascadia subduction zone, just offshore of the Pacific Northwest, ruptures. The fault has produced magnitude 9 quakes in the distant past — the most recent occurred in January 1700, spawning a tsunami that raced across the Pacific and struck Japan. In Washington, the ground near the sea fell by as much as two meters, submerging the coastline. And seismologists estimate a 1-in-3 chance of a high-end “megathrust” quake occurring along the fault in the next 50 years.

“The amount of time available with the detection [of a quake] at the coast to Puget Sound could afford tens of seconds of advanced warning time before the shaking gets to Seattle and other populated regions,” Applegate said.

The areas vulnerable to a major tsunami

ShakeAlert could be helpful when it comes to tsunamis, too. It’s already found a place in schools, such as the Ocosta School District along the South Bay in Washington, where engineers designed the elementary school to withstand a tsunami — and safely house all 700 students and staff on the roof.

Official tsunami warnings are issued by the National Tsunami Warning Center in Alaska and distributed by National Weather Service forecast offices and other agencies, via Wireless Emergency Alerts, tsunami sirens and other means.

For those in the tsunami zone experiencing an earthquake, the message is simple, said Maximilian Dixon of Washington’s Emergency Management Division. When you feel strong or long shaking or get an earthquake early-warning alert, “drop, cover and hold on” to avoid injury from the earthquake, then immediately start moving to safe high ground.

Challenges remain for tsunami scenarios

An outstanding challenge is that research has shown some locations along the Pacific Northwest coastline sit so far from safe zones that there may not be enough time to evacuate the area amid a tsunami threat.

“My modeling is able to identify the towns where there likely isn’t enough time to make it out,” said Nathan Wood, a research geographer with the United States Geological Survey in Portland, Ore., who has studied tsunami evacuations extensively.

The most dangerous areas are found along the Pacific Northwest’s low-lying outer coast, and include Washington’s Long Beach Peninsula; Westport, Wash.; Seaside, Ore.; and isolated reaches of the far Northern California coast. Perhaps the most alarming example is Ocean Shores, Wash., where a tsunami could arrive in 20 to 30 minutes and high ground is nine to 10 miles away for people on the southern tip of the peninsula.

Where natural high ground is out of reach, vertical evacuation structures can provide a refuge, and Washington has been pursuing these through an effort known as Project Safe Haven. Ocosta Elementary School’s roof structure became the first such structure in the United States, completed in 2016. This week, the nearby Shoalwater Bay Tribe will break ground on a second structure, and a third project is slated for next year in Ocean Shores.

To safely make it out of tsunami zones in lower-risk areas, residents and tourists need to understand community evacuation maps, which are available for Washington, Oregon and California.

Wood said evacuating on foot is the preferred mode because of earthquake damage to roads, downed power lines and potential traffic jams.

“I often say you need to move as quickly as you can safely,” he said. “If you are 20 blocks from the safe zone, then I definitely wouldn’t walk.”

Diana Leonard is a science writer covering natural hazards in California.