Sara K. McBride Danielle Sumy Andrea L. Llenos Grace A. Parker Jeff J. McGuire Jessie Saunders Men-Andrin Meier Douglas D. Given Robert M. deGroot 20220608 1 tabular digital data https://doi.org/10.5066/P942CLNF Sara K. McBride Danielle Sumy Andrea L. Llenos Grace A. Parker Jeff J. McGuire Jessie Saunders Men-Andrin Meier Douglas D. Given Robert M. deGroot 20220609 tabular digital data Safety Science Elsevier ShakeAlert, the earthquake early warning (EEW) system for the West Coast of the United States, attempts to provides crucial warnings before strong shaking occurs. However, because the alerts are triggered only when an earthquake is already in progress, and the alert latencies and delivery times are platform dependent, the time between these warnings and the arrival of shaking is variable. The ShakeAlert system uses, among other public alerting platforms like Google Android operating system and smartphone apps, the Federal Emergency Management Agency Integrated Public Alert & Warning System (IPAWS). IPAWS sends Wireless Emergency Alerts (WEAs) informing people via their smartphones and other mobile devices about various events, such as natural hazards, child abductions, or public health information about COVID-19. However, little is known about the IPAWS delivery latencies. Given that people may have only a few seconds of notice when they receive an alert, quantifying latencies is critical to understanding whether the IPAWS system is useful for EEW. In this study, we developed new methods to test the IPAWS distribution system's performance, both with devices in a controlled environment and as well as with a 2019 community-based feedback form, in Oakland and San Diego County, California, respectively. The controlled environment test used mobile phones (including smart and non-smart phones) and associated devices to determine alert receipt times; the community research form had participants self-report their receipt times. By triangulating the data between the controlled test environment and the community research, we determined the latency statistics as well as whether the geofence (the geographic area where the alert was intended to be sent) held broadly. We found that the latencies were similar between the two tests despite the large differences in population sizes. WEA messages were received within a median time frame of 6-12 s, and the geofence held with only a few exceptions. We use this latency to assess how the system would have performed in two large earthquakes, the 1989 M6.9 Loma Prieta and 2019 M7.1 Ridgecrest earthquakes, which both occurred near our WEA test locations. Our analysis revealed that had IPAWS been available during those earthquakes, particularly Loma Prieta, it would have provided crucial seconds of notice that damaging shaking was imminent in some locations relatively far from the epicenter. Further, we find affordable non-smart phone options can receive WEAs as fast as more expensive smartphones. Finally, our new method can be used for latency and geospatial testing going forward for IPAWS and other similar alerting systems. Data were collected to test latency in various delivery platforms for earthquake early warning 20190101 20191231 ground condition Complete None planned West Coast of United States -130.4297 -108.6328 51.6180 28.3044 ISO 19115 Topic Category biota None earthquake early warning geofence latency Wireless Emergency Alerts USGS Metadata Identifier USGS:629fbddbd34ec53d276fd57a None Wireless Emergency Alert Earthquake Early Warning geofence latency None. Please see 'Distribution Info' for details. None. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. Sara K. McBride mailing and physical

350 N. Akron Rd.

Moffett Field CA 94035 650-439-2260 skmcbride@usgs.gov limited data set with actual (true) values Yes Yes none 20220606 Oakland_Technical_Test for supplement 672022 final clean.csv Comma Separated Value (CSV) file containing data. Producer Defined Device delivery platfrom tested Producer Defined 0 34 Time Received (if identifiable) time received, therefore a measure of latency in the warning signal Producer Defined NA No Data Producer defined 4 8 SIM Card/Active? was a SIM card present in the tested device Producer Defined No no SIM card found Producer defined Not reported No SIM card reported Producer defined Yes SIM card found Producer defined San_Diego_Technical_Test for supplement 672022 clean final.csv Comma Separated Value (CSV) file containing data. Producer Defined Alert Recieved Was an alert received? Producer Defined No An alert was not received Producer defined Yes An alert was received Producer defined Not Confirmed not confirmed Producer defined Latency time of alert Producer Defined NA No Data Producer defined 8 sec Producer defined 9 sec Producer defined 10 sec Producer defined NR not recorded Producer defined 240 sec Producer defined 7 sec Producer defined 16 sec Producer defined 360 sec Producer defined 4 sec Producer defined 6 sec Producer defined Bars and Network Speed description of delivery device characteristics Producer Defined Not Report (NR) not recorded Producer defined NR not recorded Producer defined 4G four out of five bars network speed and signal strength Producer defined 4G three out of five bars network speed and signal strength Producer defined 3G one bar out of five bars network speed and signal strength Producer defined 1 bar (Speed NR) signal strength Producer defined LTE three out four bars network speed and signal strength Producer defined 5G three out of four bars network speed and signal strength Producer defined LTE four out of five bars network speed and signal strength Producer defined LTE five out of five bars network speed and signal strength Producer defined Two bars (Speed NR) signal strength Producer defined LTE three out of five bars network speed and signal strength Producer defined 4G five out of five bars network speed and signal strength Producer defined No active sim no SIM card Producer defined SIM Card/Active? Did delivery device have a SIM card? Producer Defined Yes SIM card found Producer defined No No SIM card found Producer defined Unnamed: 4 none (blank) Producer Defined << empty cell >> No Data Producer defined nan nan none none (blank) Producer Defined << empty cell >> No Data Producer defined none none Producer defined U.S. Geological Survey GS ScienceBase mailing address

Denver Federal Center, Building 810, Mail Stop 302

Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Digital Data https://doi.org/10.5066/P942CLNF None 20220608 Sara K. McBride mailing and physical

350 N. Akron Rd.

Moffett Field CA 94035 650-439-2260 skmcbride@usgs.gov FGDC Biological Data Profile of the Content Standard for Digital Geospatial Metadata FGDC-STD-001.1-1999