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Earthquake-prone LA needs a better early warning alert

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Without major changes, most Angelenos will be caught off guard when the next quake hits

Surface ruptures and offsets caused by a magnitude 7.1 earthquake are seen as the sun sets along State Route 178 between Ridgecrest and Trona, California on June 6.

During last week’s quakes in Ridgecrest, California, Los Angeles officials touted the fact that the city’s new earthquake early warning app “worked as designed,” when it delivered no warnings to users.

The lack of an alert stirred up confusion, and it highlighted an even bigger problem: The half-million people who have the app on their phones don’t know how LA’s early warning app is supposed to work—or what to expect when it is activated.

There’s a 46 percent chance that a 7.0 earthquake will strike the LA area within the next 30 years, according to the U.S. Geological Survey. Without changing the app to make it show what’s going to happen in an earthquake and why, most Angelenos will be caught off guard when the next alert is sent.

Hear Curbed urbanism editor Alissa Walker discuss the city’s earthquake early warning app on KCRW’s Greater LA.

In December, LA became the first U.S. city to launch an earthquake early warning app for smartphones, namely because the city had prioritized completing the local sensor network. Early warning systems are in place in many other seismically active countries, where they’ve delivered life-saving alerts that provide enough time for emergency agencies to prepare and people to move to safety.

After fielding complaints that app users were not alerted to last week’s two major quakes—which were felt across Los Angeles County but still below the threshold the city had set for dispatching an alert—a spokesperson from Mayor Eric Garcetti’s office confirmed to Curbed that the app’s thresholds for alerting users before events would be lowered. (In fact, the discussion had already been happening before the event.) The app will be updated by the end of July.

“Los Angeles stands on the cutting edge of seismic preparedness, and ShakeAlertLA is a critical step forward in keeping Angelenos ready and safe for the next earthquake,” says Andrea Garcia, press secretary for the mayor’s office. “By combining USGS data with our city’s mobile app technology, our early warning system will empower scientists and experts to keep developing responsive devices for the future.”

With the threshold lowered, more alerts will be sent. Now, in addition to updating the app, the city needs to provide better user education and address a much bigger challenge—making sure the other 9.5 million people living in LA County also have access to the same critical information.

Why the app didn’t issue an alert

As the first 6.4 earthquake rippled through LA County on the Fourth of July, USGS’s network of sensors had already analyzed the event and dispatched the raw ShakeAlert data that could be used in any number of early warning applications, from LA’s app, to the computers on Caltech’s campus, to other systems in place across the region.

Despite conflicting reports about the threshold at which an alert would be dispatched, USGS and the mayor’s office confirmed to Curbed that LA’s app was set to send alerts if a seismic event felt in Los Angeles County had a shaking intensity of 4 or higher.

Shaking intensity is an estimate of how strong the shaking feels at a particular location and is measured on the Modified Mercalli Intensity (MMI) scale, which is a completely different scale than magnitude.

Setting the app at 4, which signifies weak shaking, is a practical level because those events happen in LA County, but aren’t too frequent, says Robert-Michael de Groot, the national coordinator for the ShakeAlert program at USGS.

“We want to strike that delicate balance between shaking that’s potentially harmful to people versus the shaking that’s actually felt,” he says. “It could become annoying.”

Less than 36 hours after the first quake, the USGS ShakeAlert system detected what was initially considered to be an aftershock. But this 7.1 quake ended up being stronger, and parts of LA County did experience shaking intensity that was over the threshold of 4, meaning the app would have sent an alert to those areas.

That’s not what happened, but it wasn’t because of LA’s app, says de Groot. The USGS’s ShakeAlert system actually underestimated the July 5 earthquake, which was 10 times more powerful than the first.

This is something that can happen, especially for larger earthquakes, says de Groot. In the same way the magnitudes of earthquakes are revised (the 6.4 quake was originally 6.6, and the 7.1 was revised to 6.9 then back to 7.1), ShakeAlert’s data can also be updated. The first alert for the July 5 event was sent out at 8 seconds after the quake, and a second revised alert went out at 15 seconds.

Underestimating the shaking intensity is also likely to happen on the southern San Andreas Fault, where earthquakes can take some time to develop, says de Groot. “It’s a trade-off,” he says. “You can alert people more quickly, but you are only capturing that first snapshot.”

Having the app out there can help USGS improve the ShakeAlert program, which is in its very early stages, de Groot says. “Everyone is a beta tester right now. We are all part of this experience.”

The mayor’s office confirmed that the shaking intensity threshold would be changed from 4 to 3 and the magnitude threshold would be changed from 5 to 4 by the end of the month. An update pushed to iPhone users on July 5 (and to Android users on July 8) changed the threshold at which recent earthquakes would appear on a list and map from a 4 magnitude event to a 3 magnitude event.

Los Angeles Mayor Eric Garcetti Announces Early Earthquake Warning App ShakeAlertLA
Los Angeles Mayor Eric Garcetti speaks at a press conference at City Hall announcing the launch of the “ShakeAlertLA” app on January 3.
Photo by Mario Tama/Getty Images

What should happen next earthquake?

Much of the initial confusion immediately after Thursday’s first 6.4 quake was created by the app’s description, which reads: “ShakeAlertLA sends you notifications when a 5.0 or greater earthquake happens in Los Angeles County.” That language makes it sound like the earthquake has to be in LA County, which isn’t the case since some of the region’s most dangerous faults are more than 100 miles away. (Users do have to be physically in LA County for the alert to work.)

Even more crucially, the details about intensity are not included anywhere in the onboarding screens (the series of screens you click through when the app is installed) or the home screen.

Users have to click all the way through to the “about” section to see an explanation of the difference between the two numbers. There, the app’s language finally mentions shaking intensity: “ShakeAlert warnings will be issued for all earthquakes (including aftershocks) over a set magnitude threshold of 5.0 or level IV intensity.” Shaking intensity is sometimes denoted in Roman numerals to differentiate it from magnitude.

But including magnitude at all is confusing since shaking intensity is what actually affects users, argues Deanna Sellnow, chair of the communication department at the University of Central Florida’s Nicholson School of Communication and Media, who has worked on crisis messaging for earthquake early warning systems.

“There needed to be some more training about what this app means for people,” she says. “With magnitude and intensity included, it’s too complicated for people to see it and within 10 seconds know what to do.”

The app should also have the ability to play a sample event to show what the experience of receiving an alert will be like, says Sellnow. In the “about” section there is page with an image of the notification alert but nothing that simulates the experience of an earthquake, including what it looks and sounds like when it’s happening on the phone. A customized, trademarked sound that would be unique to ShakeAlert alerts is still being tested, according to USGS.

Another big part of the early warning process that was missing was an official debriefing after the event on what the app did and how to use it, says Sellnow.

“The first few hours after the initial earthquake would have been a good time for the city of Los Angeles to issue clarification on what the city’s app does and how to use it,” she says. “The debrief has to happen right after the fact, because that’s when people are most alert.”

Screenshots from the app, including the notification that will be sent before an earthquake.

From 2014 to 2016, thanks to a partnership with USGS, the city of LA had a seismic risk advisor, seismologist Lucy Jones. Technology, emergency, and public safety advisors are important, but an official science advisor would be key for a city like LA, which is confronting climate-related threats like extreme heat and wildfire in addition to earthquakes.

When the city of LA first made the app available, a city science official would have proven particularly useful. The app’s launch occurred during the shutdown of the federal government. USGS scientists were furloughed, and barred from performing nonessential tasks—like explaining how the app worked at a public event.

The city needs more than an app

Beyond an updated app, the city needs alerts to be shared in a way that doesn’t rely on smartphones. In Japan and Mexico, warnings are issued via TV and radio, as well as loudspeakers placed in public places that broadcast the alerts. Schools, shopping centers, residential communities, office buildings—all of these places could benefit from installing public alert systems.

The update of the app could also include an application that can be downloaded to smart speakers and thermostats so people with Nest and Alexa-equipped devices can hear the alerts in their residences during those crucial moments.

Early Warning Labs, which is developing the statewide QuakeAlert app using ShakeAlert data, manages the early warning alerts for local public agencies like Metro in addition to corporate campuses across California. Last week, Early Warning Labs’s Southern California partners got a 50-second warning for both earthquakes. Early Warning Labs uses a shaking intensity of 3.

The earthquakes also allowed Early Warning Labs to test a new safety feature. A Los Angeles County Fire Department station that had been fitted with a mechanical trigger automatically opened the fire station doors when the alert came in. “Firefighters were able to begin pulling the fire trucks out of the station before the shaking started,” says Josh Bashioum, cofounder of Early Warning Labs. “This was the big test we have been preparing for the last five years.”

LA can’t wait until the next earthquake to test more life-saving scenarios. It was reported Tuesday that one death might have been caused by last week’s earthquake. A 57-year-old man in Nevada who had been working under his car was found days later, crushed by his vehicle, which had fallen off its jack. The man was 100 miles from Ridgecrest, as far as most of LA was from the epicenter. If he had received an alert on a phone, radio, or public announcement system, would he have had enough time to climb out from under his Jeep?

This story was updated with a statement from the mayor’s office.