• DOI:10.1785/0220180192
• Corpus ID: 133843907

Optimizing Earthquake Early Warning Performance: ElarmS‐3

@article{Chung2019OptimizingEE,
  title={Optimizing Earthquake Early Warning Performance: ElarmS‐3},
  author={Angela I. Chung and Ivan H. Henson and Richard M. Allen},
  journal={Seismological Research Letters},
  year={2019}
}

• A. Chung, I. Henson, R. Allen
• Published 1 March 2019
• Geology
• Seismological Research Letters

The University of California Berkeley’s (UCB) Earthquake Alert Systems (ElarmS) is a network-based earthquake early warning (EEW) algorithm that was one of the original algorithms developed for theU.S. west-coast-wide ShakeAlert EEW system. Here, we describe the latest update to the algorithm, ElarmS v.3.0 (ElarmS-3 or E3). A new teleseismic filter has been developed for E3 that analyzes the frequency content of incoming signals to better differentiate between teleseismic and local earthquakes. A series of trigger filters, including amplitude-based checks and a horizontal-to-vertical ratio check, have also been added to E3 to improve the quality of triggers that are used to create events. Because of its excellent performance, E3 is now the basis for EPIC, the only ShakeAlert point-source algorithm going forward. We can therefore also use the performance of E3 described here to assess the likely performance of ShakeAlert in the coming public rollout. We should expect false events with magnitudes between M 5 and 6 less than once per year. False events with M ≥ 6 will be even less frequent, with none having been observed in testing. We do not expect to miss any M ≥ 6 onshore earthquakes, though the system may miss some large offshore events and may miss one onshore earthquake between M 5 and 6 per year. Finally, in the metropolitan regions where the station density is on the order of 10 km, we expect users 20, 30, and 40 km from an earthquake epicenter to get 3, 6, and 9 s warning, respectively, before the S-wave shaking begins. Electronic Supplement: Screenshot of the Earthquake Alert Systems (ElarmS) review tool, and example histograms and tables of algorithm performance created by the review tool.