Real-Time Performance of the PLUM Earthquake Early Warning Method during the 2019 M 6.4 and 7.1 Ridgecrest, California, Earthquakes
Abstract
We evaluate the timeliness and accuracy of ground‐motion‐based earthquake early warning (EEW) during the July 2019 M 6.4 and 7.1 Ridgecrest earthquakes. In 2018, we began retrospective and internal real‐time testing of the propagation of local undamped motion (PLUM) method for earthquake warning in California, Oregon, and Washington, with the potential that PLUM might one day be included in the ShakeAlert EEW system. A real‐time version of PLUM was running on one of the ShakeAlert EEW system's development servers at the time of the 2019 Ridgecrest sequence, allowing us to evaluate the timeliness and accuracy of PLUM's warnings for the M 6.4 and 7.1 mainshocks in real time with the actual data availability and latencies of the operational ShakeAlert EEW system. The latter is especially important because high‐data latencies during the M 7.1 earthquake degraded ShakeAlert's performance. PLUM proved to be largely immune to these latencies. In this article, we present a retrospective analysis of PLUM performance and explore three potential regional alerting strategies ranging from spatially large regions (counties), to moderate‐size regions (National Weather Service public forecast zones), to high‐spatial specificity (50 km regular geographic grid). PLUM generated initial shaking forecasts for the two mainshocks 5 and 6 s after their respective origin times, and faster than the ShakeAlert system's first alerts. PLUM was also able to accurately forecast shaking across southern California for all three alerting strategies studied. As would be expected, a cost‐benefit analysis of each approach illustrates trade‐offs between increasing warning time and minimizing the area receiving unneeded alerts. Choosing an optimal alerting strategy requires knowledge of users' false alarm tolerance and minimum required warning time for taking protective action, as well as the time required to distribute alerts to users.
Additional Information
© 2020 Seismological Society of America. Manuscript received 16 January 2020; Published online 16 June 2020. The authors wish to thank Sara McBride for sharing the results of wireless emergency alert (WEA) testing and for discussions on the connections between earthquake and weather warning systems. Luke Blair provided Geographic Information Systems (GIS) datasets. The authors would also like to thank Gail Atkinson, Shane Detweiler, Mike Diggles, Steve Hickman, Sue Hough, Ole Kaven, Evelyn Roeloffs, David Shelly, and an anonymous peer reviewer for their help with this article. 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: Earthquake source information and ShakeMaps were obtained from the U.S. Geological Survey (USGS). The event page for the M 6.4 earthquake is available at https://earthquake.usgs.gov/earthquakes/eventpage/ci38443183/executive (last accessed December 2019). The event page for the M 7.1 earthquake is available at https://earthquake.usgs.gov/earthquakes/eventpage/ci38457511/executive (last accessed December 2019). Ground‐shaking analysis was done relative to the USGS's National Earthquake Information Center (NEIC) ShakeMaps for these two earthquakes: https://earthquake.usgs.gov/earthquakes/eventpage/ci38443183/shakemap/intensity?source=us&code=ci38443183 and https://earthquake.usgs.gov/earthquakes/eventpage/ci38457511/shakemap/intensity?source=us&code=ci38457511 (both last accessed December 2019). In Figure 2, a comparison is made to the M 7.1 earthquake's ShakeMap contributed by the California Integrated Seismic Network's (CISN) Southern California Seismic Network available at https://earthquake.usgs.gov/earthquakes/eventpage/ci38457511/shakemap/intensity?source=ci&code=ci38457511 (last accessed December 2019). ShakeAlert times were obtained from log files of ShakeAlert's "Caltech production 1" server ("ci‐prod1") available at http://relm.gps.caltech.edu/eew-ci-prod1/ (last accessed December 2019). Geographic Information Systems (GIS) files for counties and National Weather Service (NWS) public forecast zones are available at https://www.weather.gov/gis/AWIPSShapefiles (last accessed December 2019). Information on NWS public forecast zones and GIS files may be obtained from https://www.weather.gov/gis/PublicZones (last accessed December 2019). Population count is the year 2020 estimate from the Center for International Earth Science Information Network (CIESIN) and National Aeronautics and Space Administration (NASA) Socioeconomic Data and Applications Center (SEDAC)'s Gridded Population of the World, Version 4 (GPWv4), available at https://doi.org/10.7927/H4X63JVC (last accessed September 2019). The real‐time PLUM logs for the MM 6.4 and 7.1 earthquakes preserving the time‐stamped observations of maximum MMI (including actual data telemetry latency and processing delays) are included in the supplemental material. The original seismograms are archived at the Southern California Earthquake Data Center (SCEDC) (https://scedc.caltech.edu/, last accessed December 2019), doi: 10.7909/C3WD3xH1. City of Los Angeles, Emergency Management Department's 2019 report, "Earthquake alerts: City of LA announces new earthquake early warning app,", is available at https://emergency.lacity.org/blog/earthquake-alerts-city-la-announces-new-earthquake-early-warning-app (last accessed December 2019). The unpublished manuscripts by A. I. Chung, M.‐A. Meier, J. Andrews, M. Böse, B. Crowell, J. McGuire, and D. Smith (2020). "ShakeAlert earthquake early warning system performance during the 2019 Ridgecrest earthquake sequence," and I. Stubailo, M. Alvarez, and G. Biasi (2020). "Latency of waveform data delivery from the Southern California Seismic Network during the 2019 Ridgecrest earthquake sequence and its effect on ShakeAlert," are submitted to Bull. Seismol. Soc. Am.Attached Files
Supplemental Material - bssa-2020021_supplement.docx
Supplemental Material - bssa-2020021_supplement_observation.dat.zip
Files
| Name | Size | Download all |
|---|---|---|
|
md5:88db4129fc8acb0d0debf5720e3878bc
|
4.6 MB | Download |
|
md5:b95240e21f8ffc4497f1bcf14cd2be55
|
986.9 kB | Preview Download |
Additional details
- Eprint ID
- 105132
- DOI
- 10.1785/0120200021
- Resolver ID
- CaltechAUTHORS:20200827-142633476
- Created
-
2020-08-27Created from EPrint's datestamp field
- Updated
-
2021-11-16Created from EPrint's last_modified field