The Limits of Earthquake Early-Warning Alerts

Downtown Los Angeles

Downtown Los Angeles Shutterstock

 

Connecting state and local government leaders

Last week’s quake near L.A. shows the promise of the West Coast seismic notification system under development. But its effectiveness will depend on those using the technology.

The magnitude 5.3 earthquake that shook parts of Southern California on Thursday may have been the region’s strongest in many years but fortunately only caused minor damage close to its epicenter offshore near the Channel Islands. It also provided a good opportunity for an earthquake early-warning system that’s been under development to show how seismic alerts can be relayed to the public in the years to come.

Thursday’s quake was centered west of Los Angeles on a strike-slip fault adjacent to Santa Cruz Island, and was felt over a wide swath of L.A., Santa Barbara and Ventura counties but due to the epicenter’s distance from populated areas, most only felt light shaking.

After the earthquake, Alissa Walker, a Los Angeles-based editor for Curbed who has been testing a quake-warning app from Santa Monica-based Early Warning Labs, reported that she had 34 seconds of lead time before the shaking reached her location.

The system used to relay the seismic warnings is built upon efforts by the U.S. Geological Survey and West Coast universities to develop ShakeAlert, which relies on networked seismometers to rapidly pinpoint the location of where an earthquake starts and transmit warnings ahead to cities and populated areas faster than damaging seismic waves can travel.

The relayed warnings, when tied into infrastructure, can automatically trigger fire station garage doors to open, prompt trains to slow down or stop and close valves on water storage tanks, though those quake-resiliency tech innovations on the West Coast have not yet been widely implemented, as they have in Japan.  

Emergency management officials in California and elsewhere on West Coast envision ShakeAlert notifications reaching the public at large through cellphones and other applications, giving people a warning in the moments before serious shaking reaches them—that could be enough time to shelter under a sturdy table to ride out the earthquake or move away from a brick-and-masonry building facade that could crumble during a major seismic event.

These early warning alerts are used in Japan and in Mexico City, where they’re are tied into public address systems in many buildings and public spaces. The U.S. has lagged in developing similar warning systems, but major progress has been made to build out the ShakeAlert network by the U.S. Geological Survey and its partner universities in West Coast states.

John Vidale at the Southern California Earthquake Center told the Los Angeles Times on Thursday that he heard the alert go off at his office at the University of Southern California, "maybe 10 seconds ahead, enough for us to puzzle about it before the shaking hit."

Although ShakeAlert isn’t yet available beyond a group of beta testers and partner organizations before the system becomes more publicly available, earthquake early-warning technology has been viewed with great promise in seismically vulnerable areas of the West Coast. In the federal spending package approved by Congress and the White House last month, champions of the earthquake early-warning network celebrated $23 million in new funding that will support continued development of the technology and its public safety applications. (The Trump administration had proposed to cut funding for more work on ShakeAlert.)

Last November, the city of Los Angeles put out a request for proposals for an app designed to relay earthquake early-warning alerts to the public with the aim of having something available by the end of this year.

For all the promise the ShakeAlert has, the system does have its limits.

Earthquake early-warning notifications are less useful the closer a recipient is to an epicenter of an earthquake. So in the case of Los Angeles, an early warning can be considerably helpful for massive quakes that start farther away from the city, like what’s expected for the next major “Big One” rupture of the southern San Andreas Fault near the Salton Sea. In that scenario, L.A. residents may get upwards of a one-minute warning before significant shaking reaches them. But L.A.’s lead time would be far shorter for quakes originating on faults in or closer to the city, like on the Hollywood Fault or in the Puente Hills southeast of downtown.

Even as ShakeAlert’s technology and ability to delivery earthquake early-warning alerts improves, there will be other challenges, especially on the user end, including potential “warning fatigue” from more frequent but smaller seismic events—not to mention accidental alerts, which have happened.

According to the U.S. Geological Survey, which late last month released a study on earthquake early-warning notifications:

When and if an advance warning is issued thus depends critically on the ground motion threshold set for alert notification. The time available to issue an alert depends on both a user’s distance to the rupturing fault and the minimum level of ground motion for which the user wants to be alerted. The amount of warning time depends most strongly on the ground-motion level that is used to trigger alerts. Longer warning times are possible if alerts are issued at lower thresholds, when only weak ground motion is expected from the earthquake.

“Using the example of an earthquake on the San Andreas Fault, that starts in northern California and ruptures toward San Francisco, alerts issued when just light shaking is expected in San Francisco could provide warning times as long as about 48 seconds in advance of when the earthquake shaking is felt there,” said Elizabeth Cochran, a USGS seismologist and coauthor of the report. “In contrast, if you wait to alert San Francisco until very strong shaking is anticipated, only 8 seconds of warning are possible.”

The authors noted that if users are willing to receive alerts and take safety actions even when it is unlikely the ground shaking will grow to become damaging, they are more likely to receive timely information they can act on. In contrast, if users prefer to limit alerts to events during which ground motion is expected to be very strong, then warning times will be short, or perhaps even arrive too late to act.

Regardless of the system’s limits, the potential benefits of ShakeAlert may not be fully realized until the next significant quake strikes a major West Coast population center, whether that’s something in Southern California, the San Francisco Bay area, or the I-5 corridor in the Pacific Northwest.

As seismologists and emergency managers say, it’s not a matter of if, but when. So it’s a race to get this lifesaving technology into the hands of the public.

PREVIOUSLY on Route Fifty:

Michael Grass is Executive Editor of Government Executive's Route Fifty and is based in Seattle.

NEXT STORY: There Is Science (and Power) Behind Effective Citizen Communication

X
This website uses cookies to enhance user experience and to analyze performance and traffic on our website. We also share information about your use of our site with our social media, advertising and analytics partners. Learn More / Do Not Sell My Personal Information
Accept Cookies
X
Cookie Preferences Cookie List

Do Not Sell My Personal Information

When you visit our website, we store cookies on your browser to collect information. The information collected might relate to you, your preferences or your device, and is mostly used to make the site work as you expect it to and to provide a more personalized web experience. However, you can choose not to allow certain types of cookies, which may impact your experience of the site and the services we are able to offer. Click on the different category headings to find out more and change our default settings according to your preference. You cannot opt-out of our First Party Strictly Necessary Cookies as they are deployed in order to ensure the proper functioning of our website (such as prompting the cookie banner and remembering your settings, to log into your account, to redirect you when you log out, etc.). For more information about the First and Third Party Cookies used please follow this link.

Allow All Cookies

Manage Consent Preferences

Strictly Necessary Cookies - Always Active

We do not allow you to opt-out of our certain cookies, as they are necessary to ensure the proper functioning of our website (such as prompting our cookie banner and remembering your privacy choices) and/or to monitor site performance. These cookies are not used in a way that constitutes a “sale” of your data under the CCPA. You can set your browser to block or alert you about these cookies, but some parts of the site will not work as intended if you do so. You can usually find these settings in the Options or Preferences menu of your browser. Visit www.allaboutcookies.org to learn more.

Sale of Personal Data, Targeting & Social Media Cookies

Under the California Consumer Privacy Act, you have the right to opt-out of the sale of your personal information to third parties. These cookies collect information for analytics and to personalize your experience with targeted ads. You may exercise your right to opt out of the sale of personal information by using this toggle switch. If you opt out we will not be able to offer you personalised ads and will not hand over your personal information to any third parties. Additionally, you may contact our legal department for further clarification about your rights as a California consumer by using this Exercise My Rights link

If you have enabled privacy controls on your browser (such as a plugin), we have to take that as a valid request to opt-out. Therefore we would not be able to track your activity through the web. This may affect our ability to personalize ads according to your preferences.

Targeting cookies may be set through our site by our advertising partners. They may be used by those companies to build a profile of your interests and show you relevant adverts on other sites. They do not store directly personal information, but are based on uniquely identifying your browser and internet device. If you do not allow these cookies, you will experience less targeted advertising.

Social media cookies are set by a range of social media services that we have added to the site to enable you to share our content with your friends and networks. They are capable of tracking your browser across other sites and building up a profile of your interests. This may impact the content and messages you see on other websites you visit. If you do not allow these cookies you may not be able to use or see these sharing tools.

If you want to opt out of all of our lead reports and lists, please submit a privacy request at our Do Not Sell page.

Save Settings
Cookie Preferences Cookie List

Cookie List

A cookie is a small piece of data (text file) that a website – when visited by a user – asks your browser to store on your device in order to remember information about you, such as your language preference or login information. Those cookies are set by us and called first-party cookies. We also use third-party cookies – which are cookies from a domain different than the domain of the website you are visiting – for our advertising and marketing efforts. More specifically, we use cookies and other tracking technologies for the following purposes:

Strictly Necessary Cookies

We do not allow you to opt-out of our certain cookies, as they are necessary to ensure the proper functioning of our website (such as prompting our cookie banner and remembering your privacy choices) and/or to monitor site performance. These cookies are not used in a way that constitutes a “sale” of your data under the CCPA. You can set your browser to block or alert you about these cookies, but some parts of the site will not work as intended if you do so. You can usually find these settings in the Options or Preferences menu of your browser. Visit www.allaboutcookies.org to learn more.

Functional Cookies

We do not allow you to opt-out of our certain cookies, as they are necessary to ensure the proper functioning of our website (such as prompting our cookie banner and remembering your privacy choices) and/or to monitor site performance. These cookies are not used in a way that constitutes a “sale” of your data under the CCPA. You can set your browser to block or alert you about these cookies, but some parts of the site will not work as intended if you do so. You can usually find these settings in the Options or Preferences menu of your browser. Visit www.allaboutcookies.org to learn more.

Performance Cookies

We do not allow you to opt-out of our certain cookies, as they are necessary to ensure the proper functioning of our website (such as prompting our cookie banner and remembering your privacy choices) and/or to monitor site performance. These cookies are not used in a way that constitutes a “sale” of your data under the CCPA. You can set your browser to block or alert you about these cookies, but some parts of the site will not work as intended if you do so. You can usually find these settings in the Options or Preferences menu of your browser. Visit www.allaboutcookies.org to learn more.

Sale of Personal Data

We also use cookies to personalize your experience on our websites, including by determining the most relevant content and advertisements to show you, and to monitor site traffic and performance, so that we may improve our websites and your experience. You may opt out of our use of such cookies (and the associated “sale” of your Personal Information) by using this toggle switch. You will still see some advertising, regardless of your selection. Because we do not track you across different devices, browsers and GEMG properties, your selection will take effect only on this browser, this device and this website.

Social Media Cookies

We also use cookies to personalize your experience on our websites, including by determining the most relevant content and advertisements to show you, and to monitor site traffic and performance, so that we may improve our websites and your experience. You may opt out of our use of such cookies (and the associated “sale” of your Personal Information) by using this toggle switch. You will still see some advertising, regardless of your selection. Because we do not track you across different devices, browsers and GEMG properties, your selection will take effect only on this browser, this device and this website.

Targeting Cookies

We also use cookies to personalize your experience on our websites, including by determining the most relevant content and advertisements to show you, and to monitor site traffic and performance, so that we may improve our websites and your experience. You may opt out of our use of such cookies (and the associated “sale” of your Personal Information) by using this toggle switch. You will still see some advertising, regardless of your selection. Because we do not track you across different devices, browsers and GEMG properties, your selection will take effect only on this browser, this device and this website.