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Published May 1, 2020 | Accepted + Supplemental Material
Journal Article Open

Earthquake Early Warning ShakeAlert 2.0: Public Rollout


The ShakeAlert earthquake early warning system is designed to automatically identify and characterize the initiation and rupture evolution of large earthquakes, estimate the intensity of ground shaking that will result, and deliver alerts to people and systems that may experience shaking, prior to the occurrence of shaking at their location. It is configured to issue alerts to locations within the West Coast of the United States. In 2018, ShakeAlert 2.0 went live in a regional public test in the first phase of a general public rollout. The ShakeAlert system is now providing alerts to more than 60 institutional partners in the three states of the western United States where most of the nation's earthquake risk is concentrated: California, Oregon, and Washington. The ShakeAlert 2.0 product for public alerting is a message containing a polygon enclosing a region predicted to experience modified Mercalli intensity (MMI) threshold levels that depend on the delivery method. Wireless Emergency Alerts are delivered for M 5+ earthquakes with expected shaking of MMI≥IV⁠. For cell phone apps, the thresholds are M 4.5+ and MMI≥III⁠. A polygon format alert is the easiest description for selective rebroadcasting mechanisms (e.g., cell towers) and is a requirement for some mass notification systems such as the Federal Emergency Management Agency's Integrated Public Alert and Warning System. ShakeAlert 2.0 was tested using historic waveform data consisting of 60 M 3.5+ and 25 M 5.0+ earthquakes, in addition to other anomalous waveforms such as calibration signals. For the historic event test, the average M 5+ false alert and missed event rates for ShakeAlert 2.0 are 8% and 16%. The M 3.5+ false alert and missed event rates are 10% and 36.7%. Real‐time performance metrics are also presented to assess how the system behaves in regions that are well‐instrumented, sparsely instrumented, and for offshore earthquakes.

Additional Information

© 2020 Seismological Society of America. Manuscript received 4 September 2019; Published online 8 April. Funding for ShakeAlert has been provided primarily by the U.S. Geological Survey (USGS), California Governor's Office of Emergency Services (Cal OES), the State of Oregon, and the Gordon and Betty Moore Foundation. The authors are grateful for the useful and comprehensive reviews of this article provided by Sarah Minson and Debi Kilb. Credit goes to Elijah Marchese for creating Figure S4. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Data and Resources: All historic event test data used here can be found at http://scedc.caltech.edu/research-tools/eewtesting.html. Some plots were made using the Generic Mapping Tools v.4.2.1 (www.soest.hawaii.edu/gmt; Wessel and Smith, 1998). Open‐source Neural Autonomic Transport System (NATS) messaging system software can be downloaded from https://nats.io. The ShakeMap scenario data are available from https://earthquake.usgs.gov/scenarios/catalog. The Hayward scenario data can be found at https://earthquake.usgs.gov/scenarios/eventpage/nclegacyhaywardrodgerscreekrchnhsm7p3_se#shakemap. The San Andreas scenario data are from https://earthquake.usgs.gov/scenarios/eventpage/sclegacyspsanandreasbbnmsmnsbssbbgcom7p9_se#shakemap. The Cascadia scenario data are from https://earthquake.usgs.gov/scenarios/eventpage/bssc2014cascadia_sub0_m9p34_se#shakemap. The other relevant data are from ShakeAlert.org and MyShakeAlert.org. All websites were last accessed in March 2020. Supplemental material contains four figures and a detailed description of ground‐motion assessment tests.

Attached Files

Accepted Version - SRL-2019245_Review.pdf

Supplemental Material - srl-2019245_supplement.pdf


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August 19, 2023
March 5, 2024