Incorporating Intensity Distance Attenuation Into PLUM Ground‐Motion‐Based Earthquake Early Warning in the United States: The APPLES Configuration

Earthquake source information, ShakeMaps, DYFI data, and ShakeAlert performance information were obtained from the U.S. Geological Survey earthquake event pages (USGS, 2017, last accessed January 2024). The ShakeMaps selected for our analysis use the most recent version of the ShakeMap software available for each earthquake, and primarily use ShakeMaps from the ShakeMap Atlas (Marano et al., 2023). The population data used in our analysis are the 2020 estimate from the Center for Internal Earth Science Information Network - CIESIN - Columbia University (2018). Information about the ShakeAlert alerts issued through the Wireless Emergency Alert system can be found at https://warn.pbs.org (last accessed January 2024). Seismic time-series data for the simulated real-time tests for the original ShakeAlert testing platform test suite (Cochran, Kohler, et al., 2018) are available at the Southern California Earthquake Data Center (SCEDC) at https://scedc.caltech.edu/data/eewtesting.html (last accessed July 2023; SCEDC, 2013). Data from the following seismic networks were used in this study: Anza regional network (AZ; Vernon, 1982), Red Sísmica del Noroeste de México (BC; Centro de Investigación Científica y de Educación Superior de Ensenada [CISESE], 1980), Berkeley Digital Seismograph Network (BDSN; BK; BDSN, 2014), Cascade Chain Volcano Monitoring (CC; Cascades Volcano Observatory/USGS, 2001), California Strong Motion Instrumentation Program (CE; California Geological Survey, 1972), Southern California Seismic Network (CI; California Institute of Technology and USGS Pasadena, 1926), Canadian National Seismograph Network (CN; Natural Resources Canada, 1975), Global Seismograph Network—IRIS/USGS (IU; Alburquerque Seismological Laboratory (ASL)/USGS, 2014), USGS Northern California Network (NC; USGS Menlo Park, 1966), Nevada Seismic Network (NN; University of Nevada, Reno, 1971), U.S. National Strong-Motion Network (NP; USGS, 1931), NEPTUNE Canada (NV; Ocean Networks Canada, 2009), Ocean Observatories Initiative (OO; Rutgers University, 2013), University of Oregon and Pacific Northwest Seismic Network (UO; University of Oregon, 1990), U.S. National Seismic Network (US; ASL/USGS, 1990), Pacific Northwest Seismic Network (UW; University of Washington, 1963). The U.S. West Coast version of the PLUM algorithm is stored in the code.usgs.gov repository following the protocol for the ShakeAlert EEW algorithms. All analysis and figures were created using Python (https://python.org). The Supporting Information S1 contains additional figures and tables pertaining to our analysis and results.