View source for ShakeAlert

{{Short description|Earthquake early warning system for the United States}}
{{For|the general topic of "shake alerts"|earthquake early warning system}}
[[File:Eew motion graphic.gif|thumb|An animation detailing how ShakeAlert functions]]

'''ShakeAlert''' is an [[earthquake warning system|earthquake early warning system]] (EEW) in the United States, developed and operated by the [[United States Geological Survey]] (USGS) and its partners.<ref name="usgsfactsheet">{{Cite journal|title=ShakeAlert: an earthquake early warning system for the United States West Coast|url=http://pubs.usgs.gov/fs/2014/3083/|journal=U.S. Geological Survey Fact Sheet 2014–3083|pages=4|date=2014-01-01|doi=10.3133/fs20143083|first1=Erin R.|last1=Burkett|first2=Douglas D.|last2=Given|first3=Lucile M.|last3=Jones|authorlink3=Lucy Jones|series=Fact Sheet|doi-access=free}}</ref> As of 2021, the system issues alerts for the country's [[West Coast of the United States|West Coast]] (specifically the states of [[California]], [[Oregon]] and [[Washington (state)|Washington]]). It is expected that the system will be expanded to other seismically active areas of the United States in the future. ShakeAlert is one of two EEW systems available in the United States, with [[Google]]'s [[Android Earthquake Alerts System]] being the other.

Similar to other earthquake early warning systems, ShakeAlert does not predict [[earthquake]]s, but rather it attempts to quickly identify a seismic event and issue an alert before widespread shaking is felt. It does this by detecting an earthquake's fast moving (but weak) [[P wave]]s, then computes the event's location and estimated magnitude, after which it issues the warning. Depending on a person's distance from the earthquake's [[epicenter]], the alert may reach them before the earthquake's slower moving (but destructive) [[S wave]]s do. These warnings can provide time for persons to take protective actions, such as "drop, cover, and hold," and for organizations to shut down transit systems, equipment, open fire station doors, and trigger specific protocols in hospitals and other sensitive work environments.

Research and development of the system began in 2006 and by the fall of 2018, the system was considered "sufficiently functional and tested" to enter phase 1 and begin issuing alerts for the West Coast states. While the warnings are generated by ShakeAlert, USGS does not send the alerts directly, instead relying on various private and public partners to distribute the messages through systems such as [[Wireless Emergency Alerts]] (WEA) and [[mobile app]]s. A statewide alert distribution system went online in California on October 17, 2019, in Oregon on March 11, 2021, and in Washington on May 4, 2021.

==Development==
[[File:ShakeAlert - example.jpg|thumb|upright=1.2|Map showing the amount of advance warning time that might be available from ShakeAlert for several plausible future earthquake scenarios.<ref name="usgsfactsheet" />]]

Initially the system has been developed to monitor and alert the [[West Coast of the United States]], an area with significant [[seismic risk]] due to the [[San Andreas fault zone]] and the [[Cascadia subduction zone]]. The West Coast system was developed by a consortium of institutions including the United States Geological Survey, the [[California Governor's Office of Emergency Services]] (Cal OES), the [[California Geological Survey]], [[California Institute of Technology]], the [[Berkeley Seismological Laboratory]] at [[University of California, Berkeley]], [[University of Washington]], [[University of Oregon]], and the [[ETH Zurich|Swiss Federal Institute of Technology in Zürich]] (ETHZ).<ref name="USGS_Implementation-Plan_2018">{{cite report|year=2018|title=Revised Technical Implementation Plan for the ShakeAlert System—An Earthquake Early Warning System for the West Coast of the United States|url=https://pubs.er.usgs.gov/publication/ofr20181155|publisher=United States Geological Survey|docket=Open-File Report 2018–1155|access-date=April 3, 2021}}</ref>

Research and development of the West Coast system (initially called CISN ShakeAlert) began in August 2006, becoming demonstrable in August 2009.<ref name="ShakeAlert_news">{{cite web|url=https://www.shakealert.org/news/|title=News|author=<!--Not stated-->|website=shakealert.org|publisher=United States Geological Survey|access-date=April 3, 2021}}</ref> In 2011, test users (mostly other seismologists) were able to access the system through the "UserDisplay" software.<ref>{{cite web|url=http://seismo.berkeley.edu/~rallen/research/shakealert.html|title=Highlights of the Berkeley contributions to ShakeAlert|last=Allen|first=Richard|website=Berkeley Seismo Lab: Richard Allen|publisher=Berkeley Seismo Lab|quote=February 2011: ShakeAlert starts providing warnings to test users}}</ref> In January 2012, [[Beta software|"beta" users]] were able to access the alerts in California. In February 2015, "beta" users were able to access the alerts in Oregon and Washington.<ref name="USGS_Implementation-Plan_2018" /><ref>{{cite web|url=https://www.washington.edu/news/2015/02/11/earthquake-early-warning-begins-testing-in-pacific-northwest/|title=Earthquake early warning begins testing in Pacific Northwest|last=Hickey|first=Hannah|date=February 11, 2015|website=UW News|publisher=University of Washington|access-date=April 3, 2021}}</ref> In February 2016, the system moved from demonstrable to Production Prototype version 1.0 in California, providing alerts to "pilot" users. In April 2017, Production Prototype version 1.2 went live, expanding the prototype to Oregon and Washington "pilot" users.<ref name="USGS_Implementation-Plan_2018" /><ref>{{cite web|url=https://www.washington.edu/news/2017/04/10/usgs-partners-launch-a-unified-west-coast-wide-earthquake-early-warning-system/|title=USGS, partners launch a unified, West Coast-wide earthquake early warning system|last=Hickey|first=Hannah|date=April 10, 2017|website=UW News|publisher=University of Washington|access-date=April 3, 2021}}</ref> (Until this time, the Oregon/Washington system had been developed and operated separately from the California system.) On September 28, 2018, version 2.0 went live,<ref>{{cite news|last=Laursen|first=Lucas|date=October 18, 2018|title=How the West Coast's New Earthquake System 'Shakealert' Will Warn You of the Next 'Big One'|url=https://fortune.com/2018/10/18/usgs-shakealert-earthquake-warning-operating/|work=Fortune|location=New York City|access-date=May 22, 2018|quote=On Sept. 28, ShakeAlert implemented a 2.0 version of its software, which causes fewer false alarms and detects a higher fraction of earthquakes.}}</ref><ref>{{cite news|last=Perkins|first=Robert|title=ShakeAlert No Longer Just a Prototype|url=https://www.caltech.edu/about/news/shakealert-no-longer-just-prototype-84133|work=Caltech News|location=Pasadena, California|date=October 17, 2018|access-date=May 22, 2021|quote=In addition, an upgrade to the software that processes data from the sensor networks was deployed on September 28. This new software should reduce the number of mistakes and missed alerts, making ShakeAlert more reliable, Given said.}}</ref> allowing the "sufficiently functional and tested" system to begin Phase 1 of alerting California, Oregon and Washington.<ref>{{cite web|url=https://www.shakealert.org/implementation/shakealert-phase-1/|title=ShakeAlert Phase 1: Version 2.0 Went Live in October 2018|author=<!--Not stated-->|year=2018|website=shakealert.org}}</ref>

Even though ShakeAlert could alert the public beginning in September 2018, the messages themselves could not be distributed until the various private and public distribution partners had completed mobile apps and made changes to various emergency alerting systems. The first publicly available alerting system was the ShakeAlertLA app, released on New Year's Eve 2018 (although it only alerted for shaking in the [[Los Angeles area]]).<ref name="LA Times_LA app available">{{cite news|last=Lin II|first=Rong-Gong|date=January 2, 2019|title=Long-awaited earthquake early warning app for L.A. can now be downloaded|url=https://www.latimes.com/local/lanow/la-me-ln-earthquake-early-warning-app-20190102-story.html|work=Los Angeles Times|location=Los Angeles|access-date=April 3, 2021}}</ref> On October 17, 2019—the thirtieth anniversary of the [[1989 Loma Prieta earthquake|Loma Prieta earthquake]]—{{abbr|Cal OES|California Office of Emergency Services}} announced a statewide rollout of the alert distribution system in California.<ref>{{cite news|last=Snibbe|first=Kurt|date=2019-10-15|title=California's earthquake early warning system is now statewide|url=https://www.mercurynews.com/2019/10/15/what-you-should-and-should-not-do-during-an-earthquake/|work=The Mercury News|access-date=2019-12-31}}</ref><ref>{{cite news|last=Calma|first=Justine|url=https://www.theverge.com/2019/10/17/20919639/california-earthquake-early-warning-system-app|title=California's earthquake warning app: how it works and what comes next|work=The Verge|date=2019-10-17|access-date=2019-12-31}}</ref><ref>{{cite web|title=Wireless Emergency Alerts|url=https://earthquake.ca.gov/wireless-emergency-alerts/|website=ca.gov|access-date=2019-12-31}}</ref> California refers to their system as the '''California Earthquake Early Warning System'''.

On March 11, 2021, a statewide alert distribution system was rolled out in Oregon.<ref name="PNSN blog_rollout">{{cite web|url=https://pnsn.org/blog/2021/03/05/oregon-rolls-out-public-alerting-for-earthquakes-on-march-11-2021|title=Oregon Rolls Out Public Alerting for Earthquakes on March 11, 2021|last=Walsh|first=Lucy|date=March 5, 2021|publisher=Pacific Northwest Seismic Network|access-date=April 3, 2021}}</ref> Rollout of the alert system for the West Coast was completed when a statewide alert distribution system went live in Washington on May 4, 2021.<ref name="Washington_EM_alerts-page">{{cite web|url=https://mil.wa.gov/alerts|title=Alert & Warning Notifications|date=May 2021|publisher=Washington Emergency Management Division|url-status=live|archive-url=https://web.archive.org/web/20210506171026/https://mil.wa.gov/alerts|archive-date=May 6, 2021|quote=On Tuesday, May 4, 2021, the ShakeAlert® Earthquake Early Warning system is live in Washington, completing the West Coast rollout of the new technology, which is capable of giving residents and visitors seconds of warning before earthquake shaking arrives.}}</ref><ref>{{cite web|url=https://www.usgs.gov/news/entire-us-west-coast-now-has-access-shakealert-earthquake-early-warning|title=Entire U.S. West Coast Now Has Access to ShakeAlert® Earthquake Early Warning|author=<!--Not stated-->|date=May 4, 2021|publisher=United States Geological Survey|access-date=May 6, 2021}}</ref><ref>{{cite web|url=https://pnsn.org/blog/2021/04/30/shakealert-rolling-out-in-washington-on-may-4|title=ShakeAlert Rolling Out in Washington on May 4|last=Lotto|first=Gabriel|date=April 30, 2021|website=PNSN blog|publisher=Pacific Northwest Seismic Network|access-date=May 6, 2021}}</ref>

===Future plans===
Of the 1,675 [[seismic station]]s needed for full implementation of the West Coast system, only 1,115 had been built or funded by April 2018 (67% of the total needed).<ref name="USGS_Implementation-Plan_2018" /> The project continues to solicit property owners for permission to place new seismic stations.<ref>{{cite web|url=http://seismo.berkeley.edu/seismo/research/host-a-station.html|title=Host A Station For Earthquake Early Warning|author=<!--Not stated-->|website=seismo.berkeley.edu|publisher=UC Berkeley Seismology Lab|access-date=April 3, 2021}}</ref>{{update inline|date=December 2021}}

Following the [[2020 Salt Lake City earthquake]], local media reported that [[Utah]] was the next state in line to get ShakeAlert.<ref>{{cite news|last=Maffly|first=Brian|date=March 29, 2020|title=What if Utahns had a few seconds' warning before an earthquake? Technology may make it possible – and save lives.|work=The Salt Lake Tribune|location=Salt Lake City, Utah|url=https://www.sltrib.com/news/environment/2020/03/29/what-if-utahns-had-few/|access-date=April 3, 2021}}</ref>

===Funding===
{{Update|section|date=April 2021}}

In 2014, USGS estimated that the West Coast system would cost $38 million to complete and $16 million per year (equivalent to ${{Format price|{{Inflation|US-GDP|38,000,000|2014|r=-7}}}}
and ${{Format price|{{Inflation|US-GDP|16,000,000|2014|r=-7}}}} in {{Inflation/year|US-GDP}}, respectively){{Inflation/fn|US-GDP}} to operate over and above the investment that had already been made in earthquake monitoring.<ref name="USGS_Implementation-Plan_2014">{{cite journal|last1=Given|first1=D.D|last2=Cochran|first2=E.S.|author-link2=Elizabeth Cochran|last3=Heaton|first3=T.|last4=Hauksson|first4=E.|last5=Vidale|first5=J.|last6=Bodin|first6=P.|title=Technical Implementation Plan for the ShakeAlert Production System—An Earthquake Early Warning System for the West Coast of the United States|journal=U.S. Geological Survey Open File Report|date=May 12, 2014|doi=10.3133/ofr20141097|url=http://pubs.usgs.gov/of/2014/1097/|access-date=2015-10-24|series=Open-File Report|doi-access=free}}</ref> By 2018, the estimates for the system's cost had grown to $39.4 million for the initial build out and $28.6 million for yearly maintenance and operation<ref name="USGS_Implementation-Plan_2018" /> (equivalent to ${{Format price|{{Inflation|US-GDP|39,400,000|2018}}}} and ${{Format price|{{Inflation|US-GDP|28,600,000|2018}}}} in {{Inflation/year|US-GDP}}, respectively).{{Inflation/fn|US-GDP}}

In December 2014, $5 million was added to the USGS budget for ShakeAlert development<ref>{{cite news|last1=Totten|first1=Sanden|title=California gets $5 million in funding for quake warning system|url=http://www.scpr.org/news/2014/12/15/48674/california-gets-funding-for-quake-warning-system/|publisher=KPCC|date=2014-12-15|access-date=2015-10-24|archive-date=2015-10-04|archive-url=https://web.archive.org/web/20151004123926/http://www.scpr.org/news/2014/12/15/48674/california-gets-funding-for-quake-warning-system/|url-status=dead}}</ref> (equivalent to ${{Format price|{{Inflation|US-GDP|5,000,000|2014|r=-7}}}} in {{Inflation/year|US-GDP}}).{{Inflation/fn|US-GDP}} This enabled USGS to purchase $1 million in seismic instrumentation and award $4 million in funding to the project partners to make the demonstration system more robust.<ref>{{Cite web|title=Earthquake early warning system moves closer to reality|url=http://www.universityofcalifornia.edu/news/earthquake-early-warning-system-moves-closer-reality|access-date=2015-08-23|date=2015-07-31}}</ref><ref>{{Cite web|title=USGS Release: USGS Awards $4 Million to Support Earthquake Early Warning System in California and Pacific Northwest (7/30/2015 12:00:00 PM)|url=http://www.usgs.gov/newsroom/article.asp?ID=4282|publisher=United States Geological Survey|access-date=2015-08-23}}</ref><ref>{{Cite web|title=Earthquake early warning system gets a $4 million boost from USGS|url=https://boingboing.net/2015/07/30/earthquake-early-warning-syste.html|website=Boing Boing|access-date=2015-08-23|first=Xeni|last=Jardin|date=2015-07-30}}</ref><ref>{{Cite web|title=Earthquake early-warning system gets a $4 million boost|url=http://www.sfgate.com/science/article/Earthquake-early-warning-system-gets-a-4-million-6416092.php|access-date=2015-08-23|website=San Francisco Chronicle|date=2015-07-30}}</ref> In 2015, more than 30 Congress members signed a joint letter urging the President to add full funding for the system to his federal budget request.<ref>{{cite news|last1=Lin|first1=Rong-gong|title=Congress members urge $16 million to fund quake early warning system|url=http://www.latimes.com/local/lanow/la-me-ln-congress-members-urge-16-million-to-fund-quake-early-warnings-20150324-story.html|access-date=2015-10-24|work=Los Angeles Times|date=2015-03-25}}</ref> The [[Gordon and Betty Moore Foundation]] has invested more than $6 million in developing the system.<ref name=GBMF>{{cite web|title=Earthquake Early-Warning System|url=https://www.moore.org/programs/science/earthquake-early-warning-system|website=Moore Foundation|access-date=2015-10-24}}</ref>

===Neighboring systems===
In August 2024, the [[Canadian Earthquake Early Warning system]] was launched by [[Natural Resources Canada]] (NRCan); this system was developed in cooperation with USGS and is based on the same software as ShakeAlert.<ref>{{Cite news|date=August 29, 2024|title=New early earthquake warning system activated in B.C.|url=https://www.cbc.ca/news/canada/british-columbia/earthquake-early-warning-system-bc-1.7308516|agency=The Canadian Press|access-date=September 30, 2024|publisher=[[CBC News]]}}</ref><ref>{{cite web|url=https://www.earthquakescanada.nrcan.gc.ca/eew-asp/system-en.php|title=Earthquake Early Warning|author=<!--Not stated-->|date=<!--Not stated-->|publisher=Natural Resources Canada|archive-url=https://web.archive.org/web/20240830135320/https://www.earthquakescanada.nrcan.gc.ca/eew-asp/system-en.php|archive-date=August 30, 2024|access-date=September 30, 2024}}</ref> While the two systems are distinct, USGS and NRCan share processing software, algorithms and real-time data.<ref>{{cite web|url=https://ohaz.uoregon.edu/project/canada-eew/|title=Earthquake Early Warning is Now Available in Canada|author=<!--Not stated-->|year=2024|website=The Oregon Hazards Lab: Projects|publisher=University of Oregon|archive-url=https://web.archive.org/web/20240829233702/https://ohaz.uoregon.edu/project/canada-eew/|archive-date=August 29, 2024|access-date=September 30, 2024}}</ref><ref>{{cite web|url=https://www.shakealert.org/wp-content/uploads/2024/06/USA-Canada_EEW_FactSheet_May_2024_English.pdf|title=Nations Collaborate on Public Safety: Earthquake Early Warning in the US and Canada|author=<!--Not stated-->|date=May 2024|website=ShakeAlert.org|publisher=United States Geological Survey|archive-url=https://web.archive.org/web/20240710112858/https://www.shakealert.org/wp-content/uploads/2024/06/USA-Canada_EEW_FactSheet_May_2024_English.pdf|archive-date=July 10, 2024|access-date=September 30, 2024}}</ref>

==Detection methods==
{{see also|Earthquake warning system}}

Full implementation of ShakeAlert on the West Coast system will require 1,675 [[seismic station]]s—1,115 in California and 560 in Oregon and Washington.<ref name="USGS_Implementation-Plan_2018" /> These stations include sensors, such as [[seismometers]], which are part of USGS's [[Advanced National Seismic System]].<ref name="USGS_Implementation-Plan_2018" /> During an earthquake, the stations send data to processing infrastructure in monitoring centers which, using various algorithms, are able to calculate the necessary information and generate alerts when needed.

Initially, ShakeAlert processing centers were capable of detecting earthquakes at an early stage because of three specific algorithms. The first algorithm was ElarmS.<ref name="ShakeAlert">{{cite web|last1=Allen|title=ShakeAlert|url=http://www.shakealert.org|access-date=October 24, 2015}}</ref> Also known as Earthquake Alarm Systems, these signals detect the P wave energy released during an earthquake. This energy, while given off quite early, does not usually cause damage. It was also the ElarmS that were responsible for roughly estimating the geographical location and size of the earthquake. Following these Elarms, empirical attenuation relations estimated how much the earth would shake in the specified region of the quake. The second algorithm was the <math>\tau_c</math>-<math>P_d</math> OnSite algorithm.<ref>{{cite journal|last1=Böse|first1=M.|last2=Hauksson|first2=Egill|last3=Solanki|first3=K.|last4=Kanamori|first4=H.|last5=Heaton|first5=T. H.|year=2009|title=Real-time testing of the on-site warning algorithm in southern California and its performance during the July 29 2008 Mw5.4 Chino Hills earthquake|url=https://authors.library.caltech.edu/14869/1/Boese2009p29010.10292008GL036366.pdf|journal=Geophysical Research Letters|volume=36|issue=5|pages=L00B03|bibcode=2009GeoRL..36.0B03B|doi=10.1029/2008GL036366|ref=Boese_2009_Real_time|doi-access=free}}</ref> By using displacement amplitude <math>P_d</math> and period <math>\tau_c</math> of the first signs of shaking, the OnSite algorithm more accurately predicted the intensity and size of the earthquake than ElarmS did.<ref name="ShakeAlert" /> The tradeoff of using these algorithms for the earliest detection possible meant having a less reliable approach than regional warning algorithms, however some argued that the added seconds to prepare are more important than reliability. Lastly, the Virtual Seismologist, known as the VS method, imitated the analysis of a human scientist in terms of capacity, but did so at a faster rate. A [[Bayesian framework]] was used with inputs of acceleration, velocity, and displacement.<ref name="ShakeAlert"/> The last step required of all these algorithms is to come together in a decision module. This decision module broadcast the probability, size, and other characteristics of the earthquake.

As of 2018, all three of these algorithms have been replaced with two new algorithms – earthquake point-source integrated code (EPIC) and finite-fault detector (FinDer).<ref name="USGS_Implementation-Plan_2018" />

In 2024, Global Navigation Satellite System (GNSS) data was added to ShakeAlert to aid in the characterization of large magnitude earthquakes.<ref>{{Cite web|last=Johnson|first=Scott|date=2024-06-05|title=GPS stations are now part of the ShakeAlert® Earthquake Early Warning System network|url=https://www.earthscope.org/news/gps-now-part-of-shakealert/|access-date=2024-06-06|website=EarthScope Consortium|language=en-US}}</ref> The algorithm, GFAST (Geodetic First Approximation of Size and Timing), uses the peak ground displacement recorded at permanent GPS stations to determine magnitude.<ref>{{Cite journal|last=Crowell|first=Brendan W.|last2=Schmidt|first2=David A.|last3=Bodin|first3=Paul|last4=Vidale|first4=John E.|last5=Gomberg|first5=Joan|last6=Renate Hartog|first6=J.|last7=Kress|first7=Victor C.|last8=Melbourne|first8=Timothy I.|last9=Santillan|first9=Marcelo |last10=Minson |first10=Sarah E.|last11=Jamison|first11=Dylan G.|date=2016-06-08|title=Demonstration of the Cascadia G‐FAST Geodetic Earthquake Early Warning System for the Nisqually, Washington, Earthquake|url=https://doi.org/10.1785/0220150255|journal=Seismological Research Letters|volume=87|issue=4|pages=930–943|doi=10.1785/0220150255|issn=0895-0695}}</ref> GFAST was developed by researchers from the [[Pacific Northwest Seismic Network]] at [[University of Washington]]. GFAST receives initial earthquake source information (origin time and epicenter) from EPIC or FinDer. Considerable logic was added to ShakeAlert to combine magnitude estimates from all three ShakeAlert algorithms<ref>{{Cite journal|last=Murray|first=Jessica R.|last2=Crowell|first2=Brendan W.|last3=Murray|first3=Mark H.|last4=Ulberg|first4=Carl W.|last5=McGuire|first5=Jeffrey J.|last6=Aranha|first6=Mario A.|last7=Hagerty|first7=Mike T.|date=2023-02-23|title=Incorporation of Real-Time Earthquake Magnitudes Estimated via Peak Ground Displacement Scaling in the ShakeAlert Earthquake Early Warning System|url=https://doi.org/10.1785/0120220181|journal=Bulletin of the Seismological Society of America|volume=113|issue=3|pages=1286–1310|doi=10.1785/0120220181|issn=0037-1106}}</ref> to ensure robustness of solutions.

==Alert distribution==
[[File:ShakeAlert.jpg|thumb|upright=1.5|Example of warning issued by ShakeAlert.<ref name="usgsfactsheet" />]]
[[File:ShakeAlert - Alert Thresholds as of June 2021.jpg|thumb|upright=1.5|USGS graphic showing thresholds for public alerts from ShakeAlert.]]

ShakeAlert warnings are sent to both institutional users and the general public through a variety of distribution methods; this includes messages via cell phones, television and radio. These alerts may give people time to take protective actions like "[[drop, cover and hold on]]", preventing injuries caused by falling debris. Various automated systems can listen for the alerts and stop [[public transport]] systems, prevent cars from entering bridges or tunnels, automatically shut down industrial systems and [[gas line]]s, and trigger specific protocols in hospitals and other sensitive work environments.

===Institutional users===
[[Bay Area Rapid Transit]] (BART) was an early user of ShakeAlert, initially connecting to the system in 2012 (when it was still in development). BART uses the system to automatically brake its trains when shaking threatens the [[San Francisco Bay Area]].<ref>{{cite web|url=https://www.bart.gov/news/articles/2012/news20120927|title=BART teams with UC Berkeley to adopt earthquake early warning system|author=<!--Not stated-->|date=September 27, 2012|website=Bay Area Rapid Transit: News|publisher=Bay Area Rapid Transit|access-date=April 3, 2021|quote=Thanks to assistance from the Berkeley Seismological Laboratory, the San Francisco Bay Area Rapid Transit system can now automatically brake trains when earthquakes threaten to rattle the Bay Area, allowing perhaps tens of seconds to a minute for trains to slow down before the ground starts to shake.}}</ref>

By 2015, organizations enrolled in the beta test user program included: {{abbr|CalOES|California Office of Emergency Services}} Warning Center, [[LA County Fire]], {{abbr|LA City OEM|City of Los Angeles Office of Emergency Management}}, [[Amgen]], [[LADWP]], [[Metrolink (California)|Metrolink]], [[CalTrans]] and [[Disneyland]].<ref>{{cite web|url=http://www.shakealert.org/shakealert-test-users/|title=ShakeAlert Test Users|publisher=ShakeAlert|access-date=April 3, 2021|url-status=unfit|archive-url=https://web.archive.org/web/20150309093942/http://www.shakealert.org/shakealert-test-users/|archive-date=March 9, 2015}}</ref> Additional institutional users were able to access alerts from the system, after ShakeAlert version 2.0 went live at the end of September 2018.<ref>{{cite web|url=https://news.berkeley.edu/story_jump/earthquake-early-warning-milestone-shakealert-rolled-out-to-entire-bay-area/|title=Earthquake early warning milestone: ShakeAlert rolled out to entire Bay Area|last=Sanders|first=Robert|date=October 8, 2018|website=Berkeley News|publisher=UC Berkeley|access-date=May 22, 2021}}</ref>

===Cell phone alerts===
====Mobile apps====
As of 2023, there are two [[mobile app]]s licensed to work with ShakeAlert: ''MyShake'', developed by UC Berkeley, and ''SD Emergency'', developed by [[San Diego County, California|San Diego County]].<ref>{{cite web|url=https://www.usgs.gov/faqs/how-do-i-sign-shakealertr-earthquake-early-warning-system|title=How do I sign up for the ShakeAlert® Earthquake Early Warning System?|author=<!--Not stated-->|publisher=United States Geological Survey|access-date=December 2, 2023}}</ref>

=====MyShake=====
MyShake was released in February 2016. Initially the app did not issue alerts, but instead used a phone's [[accelerometer]]s to record shaking from an earthquake and send the data back to UC Berkeley for analysis, thereby creating a crowdsourced global seismic network.<ref>{{cite web|url=https://news.berkeley.edu/2016/02/12/new-app-turns-smartphones-into-worldwide-seismic-network/|title=New app turns smartphones into worldwide seismic network|last=Sanders|first=Robert|date=February 12, 2016|website=Berkeley News|publisher=UC Berkeley|access-date=April 3, 2021|quote=UC Berkeley scientists today are releasing a free Android app that taps a smartphone’s ability to record ground shaking from an earthquake, with the goal of creating a worldwide seismic detection network that could eventually warn users of impending jolts from nearby quakes.}}</ref> On October 17, 2019, a new version of the app was announced, which would also provide alerts from ShakeAlert to users in California, while allowing users outside the state to continue being part of the crowdsourced global network.<ref name="Berkeley Press Release_2019">{{cite web|url=https://news.berkeley.edu/2019/10/17/california-rolls-out-first-statewide-earthquake-early-warning-system/|title=California rolls out first statewide earthquake early warning system|last=Sanders|first=Robert|date=October 17, 2019|website=Berkeley News|publisher=UC Berkeley|access-date=April 3, 2021}}</ref> The app began providing earthquake alerts in Oregon on March 11, 2021<ref>{{Cite tweet|user=USGS_ShakeAlert|number=1369748115402596353|title=UPDATE! #ShakeAlert partner @MyShakeApp begins alert delivery to mobile devices in Oregon on 3/11.}}</ref> and in Washington state on January 26, 2022.<ref>{{cite web|url=https://mil.wa.gov/news/myshake-earthquake-early-warning-app-now-available|title=MyShake Earthquake Early Warning app now available|author=Washington Military Administrator|date=January 26, 2022|website=mil.wa.gov|publisher=Washington Military Department|access-date=March 22, 2022}}</ref>

MyShake only delivers alerts for earthquakes exceeding M<sub>W</sub>4.5 and that will produce a [[shaking intensity]] greater than three.<ref name="Berkeley Press Release_2019" />

=====SD Emergency=====
On August 26, 2021, officials from the County of San Diego and USGS announced that the "ShakeReadySD" feature had been added to the county's SD Emergency app, which would provide ShakeAlert warnings throughout California.<ref>{{cite news|last=Moe|first=Yvette Urrea|date=August 25, 2021|title=SD Emergency App Users Now Can Have Earthquake Early Warning|url=https://www.countynewscenter.com/sd-emergency-app-users-now-can-have-earthquake-early-warning/|publisher=County of San Diego Communications Office|access-date=March 22, 2022}}</ref><ref>{{cite news|last=Gregorio-Nieto|first=Brenda|date=August 25, 2021|title=SD County Updates Emergency App to Include Earthquake Warning System|url=https://www.nbcsandiego.com/news/local/sd-county-updates-emergency-app-to-include-earthquake-warning-system/2702241/|work=NBC San Diego|location=San Diego, California|access-date=March 22, 2022}}</ref>

=====Former apps=====
======QuakeAlertUSA======
QuakeAlertUSA had been under development (and open to beta users),<ref>{{cite press release|author=<!--Not stated-->|title=Earthquake Early Warning App "QuakeAlert" to be tested by USGS, Caltech and other university researchers.|url=https://earlywarninglabsllc.newswire.com/news/earthquake-early-warning-app-quakealert-to-be-tested-by-3514949|publisher=Early Warning Labs|agency=Newswire|date=May 26, 2015|access-date=April 3, 2021}}</ref> by Early Warning Labs, LLC, for several years before being publicly released on January 21, 2020 (at which time it only provided earthquake alerts in California).<ref>{{Cite tweet|user=EarlyWarningLab|number=1219750872642572288|title=#QuakeAlertUSA is NOW OPEN to everyone in #California!}}</ref> The app began providing earthquake alerts in Oregon on March 11, 2021.<ref>{{Cite tweet|user=PNSN1|number=1370072163689005061|title=Oregon, today's the day!}}</ref> The QuakeAlertUSA app was decommission on November 6, 2023, so that the company could focus on its commercial earthquake response services.<ref>{{cite news|last=Woolfolk|first=John|date=November 7, 2023|title=This early-warning earthquake app has been retired, but here are others that Californians can still rely on|url=https://www.mercurynews.com/2023/11/07/this-early-warning-earthquake-app-has-been-retired-but-here-are-others-that-californians-can-still-rely-on/|work=The Mercury News|location=San Jose, California|access-date=December 2, 2023}}</ref>

QuakeAlertUSA delivered alerts for earthquakes exceeding [[Moment magnitude scale|M<sub>W</sub>]]4.5 and that produced a [[shaking intensity]] greater than three. (Settings could be changed to require higher intensity earthquakes before alerting the user.)<ref name="LA Times_QuakeAlertUSA_2020">{{cite news|last=Lin II|first=Rong-Gong|date=February 12, 2020|title=California's new early warning earthquake app features a shaking countdown|url=https://www.latimes.com/california/story/2020-02-12/californias-new-early-warning-earthquake-app-features-a-shaking-countdown|work=Los Angeles Times|location=Los Angeles|access-date=April 3, 2021}}</ref>

======ShakeAlertLA======
ShakeAlertLA, was developed by the [[City of Los Angeles]] and [[AT&T]]. This app, which only warned of shaking in the Los Angeles County area, was made available to the general public at the end of 2018,<ref name="LA Times_LA app available" /> but was retired after December 31, 2020.<ref>{{cite news|last=de Leon|first=Kristine|date=December 23, 2020|title=L.A. retires ShakeAlertLA, transitions to statewide earthquake warning app|url=https://ktla.com/news/local-news/l-a-retires-shakealertla-transitions-to-statewide-earthquake-warning-app/|publisher=KTLA|location=Los Angeles|access-date=April 3, 2021}}</ref><ref>{{cite web|url=https://earthquake.lacity.org/shakealertla|title=Download the MyShake Earthquake Early Warning App|author=<!--Not stated-->|year=2020|website=earthquake.lacity.org|publisher=City of Los Angeles|access-date=April 3, 2021|url-status=unfit|archive-url=https://web.archive.org/web/20210118082445/https://earthquake.lacity.org/shakealertla|archive-date=January 18, 2021}}</ref>

====Wireless Emergency Alerts====
In the United States, the [[Wireless Emergency Alerts]] (WEA) system is used to disseminate emergency alerts (such as [[AMBER alert]]s) to compatible mobile devices within a predefined area. ShakeAlert is capable of sending alerts to the [[Integrated Public Alert and Warning System]] (run by the [[Federal Emergency Management Agency]]), which then—through the WEA system—distributes messages to phone service providers who ultimately deliver the alert to their customers' devices.<ref name="ShakeAlert Website_WEA">{{cite web|url=https://www.shakealert.org/implementation/wea/|title=Wireless Emergency Alert system|website=shakealert.org|publisher=United States Geological Survey|access-date=April 3, 2021}}</ref>

WEA alerts are simple text messages,<ref name="ShakeAlert Website_WEA" /> unlike the alerts sent by some mobile apps (as select apps include graphics with estimated intensity and arrival time of shaking). WEA alerts may also arrive more slowly than alerts from apps.<ref name="LA Times_QuakeAlertUSA_2020" /> Although unlike apps which must be downloaded, phones can receive WEA alerts automatically as long as emergency alerts are turned on in the device's settings.<ref>{{cite web|url=https://www.oregon.gov/oem/hazardsprep/pages/orshakealert.aspx|title=ShakeAlert® in Oregon|author=<!--Not stated-->|year=2021|website=oregon.gov|publisher=Oregon Office of Emergency|access-date=April 3, 2021|quote=No sign up is required to receive ShakeAlert notifications, and no action needs to be taken other than enabling emergency alerts on your cell phone.}}</ref>

ShakeAlert messages have been delivered via WEA in California since October 17, 2019,<ref>{{cite news|author=<!--Staff writer(s)/no by-line.-->|title=Gov. Newsom launches California earthquake alert app|url=https://www.cbs8.com/article/news/local/california-earthquake-alerts-to-become-available-statewide/509-e08ab3e4-fe00-41d6-a549-0d7a0608158f|work=CBS8|location=San Diego, California|date=October 17, 2019|access-date=April 3, 2021}}</ref> in Oregon since March 11, 2021,<ref name="PNSN blog_rollout" /> and in Washington since May 4, 2021.<ref name="Washington_EM_alerts-page" />

WEA alerts are only sent for M<sub>W</sub>5.0 or larger earthquakes.<ref name="ShakeAlert Website_WEA" />

====Push notifications====
On August 11, 2020, [[Google]] announced that it had partnered with USGS, allowing its [[Android operating system]] to distribute ShakeAlerts for California. The alerts are displayed using the operating system's built-in notification feature, which does not require an app or a message from the WEA system.<ref>{{cite web|url=https://blog.google/products/android/earthquake-detection-and-alerts/|title=Earthquake detection and early alerts, now on your Android phone|last=Stogaitis|first=Marc|date=August 11, 2020|website=Google blog|publisher=Google|access-date=April 3, 2021}}</ref><ref>{{cite web|url=https://source.asce.org/android-phones-now-offer-earthquake-detection-alerts/|title=Android phones now offer earthquake detection, alerts|last=Cardno|first=Catherine A.|date=November 30, 2020|website=source.asce.org|publisher=Civil Engineering Source|access-date=April 3, 2021|quote=Google also launched in August an earthquake early warning system in a regionally specific collaboration with the United States Geological Survey and the California Governor’s Office of Emergency Services, according to Stogaitis.}}</ref> The feature was also rolled out on March 11, 2021, in Oregon,<ref name="PNSN blog_rollout" /> and in Washington in the days following May 4, 2021.<ref name="Washington_EM_alerts-page" />

As of 2021, [[iOS|Apple's iOS]] does not include a similar built-in notification system for ShakeAlert. Conversations between USGS and Apple have occurred, but no resolution has been reached.<ref name="Washington_rollout_SeattleTimes">{{cite news|last=Sandi|first=Doughton|date=May 3, 2021|title=Cellphone earthquake alerts debut in Washington – with a catch|work=The Seattle Times|location=Seattle, Washington|url=https://www.seattletimes.com/seattle-news/science/cellphone-earthquake-alerts-debut-in-washington-with-a-catch/|access-date=May 6, 2021}}</ref> However, these devices can still receive earthquake alerts through WEA messaging, or, depending on the state, through apps.

==Past performance==
===Events during system development===
====2014 California earthquakes====
The system issued alerts for several significant southern California earthquakes in 2014 including a M<sub>W</sub>4.4 event in [[Encino, Los Angeles|Encino]], a M<sub>W</sub>4.2 event in [[Westwood, Los Angeles|Westwood]], and a M<sub>W</sub>5.1 event in [[La Habra, California|La Habra]].<ref name = LATimes2>{{cite news|last1=Xia|first1=Rosanna|title=Earthquake early alert system ready to expand in California|url=http://www.latimes.com/local/california/la-me-1123-earthquake-early-warning-20141123-story.html|work=Los Angeles Times|date=2014-11-23}}</ref>

It also issued a warning 5.4 seconds after the beginning of the M<sub>W</sub>6.0 [[2014 South Napa earthquake|South Napa earthquake]] that hit the [[Napa County, California|Napa]] region on August 24, 2014.<ref name="AGU">{{cite journal|last1=Allen|first1=Richard M.|last2=Given|first2=Douglas D.|last3=Heaton|first3=Thomas H.|last4=Vidale|first4=John E.|year=2014|title=Successful ShakeAlert Performance for the Napa Quake|journal=2014 AGU Fall Meeting|location=San Francisco, California|volume=2014|issue=S44D–01|pages=S44D–01|bibcode=2014AGUFM.S44D..01A}}</ref> Although it was initially reported that the system provided 10 seconds of warning before the S wave arrived in [[Berkeley, California|Berkeley]],<ref name="cbs2">{{cite news|title=Experimental warning system gave 10-second alert before California earthquake|publisher=[[CBS News]]|date=2014-08-24|url=http://www.cbsnews.com/news/experimental-warning-system-gave-10-second-alert-before-quake-hit/|archive-url=https://web.archive.org/web/20140825234110/http://www.cbsnews.com/news/experimental-warning-system-gave-10-second-alert-before-quake-hit/|archive-date=25 August 2014|url-status=live}}</ref><ref>{{Cite web|title=In Latest Calif. Earthquake, Shake Alert Tests Its Legs|url=https://www.npr.org/2014/08/25/343203813/in-latest-calif-earthquake-shake-alert-tests-its-legs|publisher=NPR|access-date=2015-08-23|first=Melissa|last=Block}}</ref> subsequent information showed that this was in error and the warning arrived 5 seconds before the S wave in Berkeley.<ref name="AGU" /> This means the S waves had already arrived in Napa and [[Vallejo, California|Vallejo]] when the warning was issued. [[San Francisco]] received 8 seconds warning.<ref name = LATimes2 />

====2019 Ridgecrest earthquakes====
ShakeAlert generated warnings for both the July 5 M<sub>W</sub>6.4 and July 5 M<sub>W</sub>7.1 [[2019 Ridgecrest earthquakes|Ridgecrest earthquakes]].

Although not yet publicly available, beta users of the QuakeAlert mobile app received warnings on their phones.<ref>{{Cite web|url=https://www.prweb.com/releases/early-warning-labs-delivers-the-only-commercially-licensed-shakealerts-to-people-amp-automated-systems-across-southern-california-during-recent-m6-4-amp-m7-1-earthquakes-827814978.html|title=Early Warning Labs Delivers the Only Commercially Licensed ShakeAlerts to People & Automated Systems Across Southern California during Recent M6.4 & M7.1 Earthquakes}}</ref> On average, the app's beta users received a warning of 45 seconds for both earthquakes.<ref name="LA Curbed 2019 earthquake">{{Cite web|url=https://la.curbed.com/2019/7/4/20682446/earthquake-los-angeles-fourth-of-july-shake-alert|title=Two large earthquakes rattle LA—but where was the early warning?|date=2019-07-04}}</ref> The only publicly available app (at the time), ShakeAlertLA, did not send an alert during the earthquakes.<ref>{{Cite web|last1=Dowd|first1=Katie|date=2019-07-04|title=ShakeAlert fails to send earthquake warning for big SoCal quake|url=https://www.sfgate.com/bayarea/article/california-earthquake-la-shakealert-warning-14072013.php|access-date=2019-07-04|website=San Francisco Chronicle}}</ref> According to the City of Los Angeles, the system did not send alerts due to the estimated shaking in the Los Angeles area being below the activation threshold.<ref name="LA Curbed 2019 earthquake" />

===Events following general availability===
====2019 Cholame earthquake====
On December 17, 2019, the then recently released MyShake app sent its first alert for a M<sub>W</sub>4.3 earthquake in the Cholame Valley. (Even though the earthquake was below the M<sub>W</sub>4.5 threshold, a warning was still transmitted through the app, because preliminary readings measured the magnitude as 4.8.)<ref>{{Cite web|url=https://www.latimes.com/california/story/2019-12-18/a-milestone-earthquake-early-warning-system-sends-first-public-alert-to-smartphones-in-california|title=A milestone: Earthquake early warning system sends first public alert to smartphones in California|date=2019-12-18|website=Los Angeles Times|language=en-US|access-date=2020-01-08}}</ref> No Wireless Emergency Alert was transmitted because the magnitude of the earthquake was below the 5.0 threshold.

====2021 Antelope Valley earthquake====
The 2021 Antelope Valley earthquake occurred in a rural area near the California–Nevada border. Due to the remoteness of the area, there were few sensor stations near the earthquake and this resulted in the M<sub>W</sub>6.0 earthquake incorrectly being split into "phantom quakes" by the system – a M<sub>W</sub>4.8 near [[Lee Vining, California|Lee Vining]], M<sub>W</sub>4.8 near [[Stockton, California|Stockton]], and M<sub>W</sub>4.3 near [[Mammoth Lakes, California|Mammoth Lakes]]. Additionally, it took the system 25 seconds to declare an earthquake and issue an alert.<ref>{{cite news|last=Krieger|first=Lisa M.|date=July 9, 2021|title=What ShakeAlert got wrong – and right – about big Antelope Valley quake|work=The Mercury News|location=San Jose, California|url=https://www.mercurynews.com/2021/07/09/what-shakealert-got-wrong-and-right-about-big-antelope-valley-quake/|access-date=10 July 2021}}</ref><ref>{{Cite tweet|user=USGS_ShakeAlert|number=1413515422855405580|title=ShakeAlert "split" yesterday’s magnitude 6.0 Antelope Valley quake}}</ref> While mobile apps received the alert, the warning was for an earthquake identified as M<sub>W</sub>4.8 near Stockton (an incorrect magnitude and location). No Wireless Emergency Alert was transmitted because the system initially estimated the magnitude to be below the required M<sub>W</sub>5.0 threshold (finalized reports showed the earthquake had actually exceeded the threshold for a WEA alert).<ref>{{cite web|url=https://www.usgs.gov/news/magnitude-60-earthquake-california?qt-news_science_products=2#qt-news_science_products|title=Magnitude 6.0 Earthquake in California|author=<!--Not stated-->|date=July 8, 2021|publisher=United States Geological Survey|access-date=July 10, 2021}}</ref>

====2022 Ferndale earthquake====
About 270,000 phones were alerted during the magnitude 6.4 December [[2022 Ferndale earthquake]].<ref>{{Cite web|agency=Associated Press|date=December 21, 2022|title=Tens of thousands without power after California earthquake|url=https://www.bostonglobe.com/2022/12/20/nation/magnitude-64-earthquake-shakes-parts-northern-california/|access-date=2023-10-16|website=The Boston Globe|language=en-US}}</ref>

==See also==
* [[Earthquake Early Warning (Japan)]]

==References==
{{cols|colwidth=26em}}
{{reflist}}
{{colend}}

==External links==
* {{Official website|https://www.shakealert.org/}}
* [https://earthquake.ca.gov Earthquake Warning California]
* [https://myshake.berkeley.edu MyShake]
* [https://www.alertsandiego.org/en-us/preparedness/SDEmergencyApp.html SD Emergency]
* [https://www.youtube.com/watch?v=WWl3m4OyU44 ShakeAlert—Earthquake Early Warning. How does it work?] – [[IRIS Consortium]]

[[Category:Earthquake early warning systems]]
[[Category:Earthquake engineering]]
[[Category:United States Geological Survey]]
[[Category:Emergency population warning systems]]