Status and performance of the ShakeAlert® earthquake early warning system: 2019-2023
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Abstract
The U.S. Geological Survey (USGS)‐operated ShakeAlert® system is the United States West Coast earthquake early warning system (Given et al., 2018). In this study we detail ShakeAlert’s performance during some of the largest events seen by the system thus far. Statewide public alerting using ShakeAlert messages was authorized in California in October 2019. Over the next few years, public alerts were expanded into Oregon and then into Washington (U.S. Geological Survey, 2024). ShakeAlert source results are routinely compared to the USGS Comprehensive Catalog (ComCat; Guy et al., 2015; U.S. Geological Survey, Earthquake Hazards Program, 2017), which contains the earthquake location and magnitude determined using complete waveform data. M 4.5 and larger is the threshold used for public alerting and was deliberately set below the level where damage is likely to compensate for cases where the system underestimates the magnitude. Between 17 October 2019 and 1 September 2023, the ShakeAlert system created 95 events with maximum magnitude estimates of M ≥4.5, the public alerting threshold. 94 of the 95 events were due to real earthquakes. Seven were categorized “false” per ShakeAlert’s internal definition that there was no matching catalog event within 100 km and 30 s of origin time; however, all but one of these were real earthquakes that were poorly located, primarily because they were at the edges of the seismic network. Three detected events were labeled “missed” because they were very poorly located (>100 km location error). In addition, the system did not produce solutions for four ComCat events M ≥4.5 (U.S. Geological Survey, Earthquake Hazards Program, 2017), which were all at the edge of the alerting and network boundaries. The ShakeAlert system has accurately detected the majority of earthquakes that have occurred within the operational region since completing the public rollout, and alerts from the system have been delivered to millions of cell phone users throughout the West Coast.
Study Area
Publication type | Article |
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Publication Subtype | Journal Article |
Title | Status and performance of the ShakeAlert® earthquake early warning system: 2019-2023 |
Series title | Bulletin of the Seismological Society of America |
DOI | 10.1785/0120230259 |
Volume | 114 |
Issue | 6 |
Publication Date | August 16, 2024 |
Year Published | 2024 |
Language | English |
Publisher | Seismological Society of America |
Contributing office(s) | Earthquake Science Center |
Description | 22 p. |
First page | 3041 |
Last page | 3062 |
Country | United States |
State | California, Oregon, Washington |