Thakoor, Kaveri and Andrews, Jennifer and Hauksson, Egill and Heaton, Thomas (2019) From Earthquake Source Parameters to Ground‐Motion Warnings near You: The ShakeAlert Earthquake Information to Ground‐Motion (eqInfo2GM) Method. Seismological Research Letters, 90 (3). pp. 1243-1257. ISSN 0895-0695. doi:10.1785/0220180245. https://resolver.caltech.edu/CaltechAUTHORS:20190320-100917720
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Abstract
We present a new near‐real‐time method for converting earthquake source parameters into ground motion (GM) at locations across the west coast of the United States. This method, called earthquake information to ground motion (eqInfo2GM), has been implemented as part of the ShakeAlert earthquake early warning (EEW) system and makes estimated GM accessible to users on the EEW timeframe of seconds, as the U.S. Geological Survey ShakeMap does at higher resolution and accuracy in the minutes following a seismic event. Whereas the higher fidelity ShakeMap comes at the cost of longer processing times, eqInfo2GM effectively provides a predicted ShakeMap before shaking arrives at many locations. We describe key design details, including ground‐motion prediction equations (GMPEs) implemented, modifications made to optimize for speed, and formats created for conveying GM severity. The GM output format determines added latency and reflects a trade‐off between speed and accuracy; for our test earthquake data set, added latency is in the 0.01–1.5 s range after earthquake source parameters have been generated. GMPE implementations are validated against predicted ShakeMaps (without observations), with almost all events showing minimal mean shaking intensity level differences, reflecting variations only in treatment of source distances and VS30 data. Comparison against ShakeMaps computed with observations (a proxy for true GM) show larger differences, demonstrating the challenges of working in the EEW timeframe, when full source characterization and peak ground motion observations are both unavailable. Although specific configurations and features of the method will evolve as the needs of the EEW user community become evident, eqInfo2GM is expected to improve the overall utility of EEW alerts by providing end users with estimates of predicted local GM hazard. Such near‐real‐time estimates will enable users to decide more accurately what action to take to reduce the impact of imminent, potentially damaging shaking.
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| Additional Information: | © 2019 Seismological Society of America. Published Online 20 March 2019. Data and Resources: The testing suite of historic earthquakes used for offline testing of earthquake information to ground motion (eqInfo2GM) comes from the Southern California Earthquake Data Center (SCEDC, 2013; http://scedc.caltech.edu/research-tools/eewtesting.html). The ShakeMap scenario data from the U.S. Geological Survey (USGS) webpages are available at https://earthquake.usgs.gov/scenarios/catalog/. The Hayward scenario (https://earthquake.usgs.gov/scenarios/eventpage/nclegacyhaywardrodgerscreekrchnhsm7p3_se#shakemap), San Andreas scenario (https://earthquake.usgs.gov/scenarios/eventpage/sclegacyspsanandreasbbnmsmnsbssbbgcom7p9_se#shakemap), and Cascadia scenarios (deep and shallow) (https://earthquake.usgs.gov/scenarios/eventpage/bssc2014cascadia_sub0_m9p34_se#shakemap) are the other sources used in this article. Plots in Figures 2–4 were generated using Python. All websites were last accessed on August 2018. The authors would like to convey our profound thanks to Garret Hartman and Claude Felizardo for countless valuable discussions throughout the creation of the earthquake information to ground‐motion (eqInfo2GM) module. The authors are tremendously grateful to Debbie Smith and Steve Guiwits for providing ShakeMaps for eqInfo2GM validation analysis for point‐source as well as finite‐fault scenarios. The authors’ gratitude goes to the code review panel (Claude Felizardo, Garret Hartman, Ivan Henson, Angela Chung, Renate Hartog, Steve Guiwits, Victor Kress, Debbie Smith, and Monica Kohler) and to Monica Kohler and Doug Given for their insightful review of this article. The authors would also like to thank Elizabeth Cochran, Sarah Minson, and Annemarie Baltay Sundstrom for useful ground‐motion prediction equation (GMPE) discussions, and all members of the earthquake early warning (EEW) teams from Caltech, U.S. Geological Survey (USGS), and across the west coast. Many thanks go to the members of the USGS Joint Committee on Communication, Education, and Outreach, especially Bob de Groot and Margaret Vinci for facilitating these dialogues, as well as the end‐user groups who provided feedback on potential use cases of eqInfo2GM. Finally, the authors are grateful to the manuscript reviewers for their detailed and thoughtful feedback, which helped improve this work. Funding for this project came from the Gordon and Betty Moore Foundation and from the U.S. Geological Survey. | |||||||||
| Group: | Seismological Laboratory | |||||||||
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| Issue or Number: | 3 | |||||||||
| DOI: | 10.1785/0220180245 | |||||||||
| Record Number: | CaltechAUTHORS:20190320-100917720 | |||||||||
| Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20190320-100917720 | |||||||||
| Official Citation: | Kaveri Thakoor, Jennifer Andrews, Egill Hauksson, Thomas Heaton; From Earthquake Source Parameters to Ground‐Motion Warnings near You: The ShakeAlert Earthquake Information to Ground‐Motion (eqInfo2GM) Method. Seismological Research Letters ; 90 (3): 1243–1257. doi: https://doi.org/10.1785/0220180245 | |||||||||
| Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | |||||||||
| ID Code: | 93983 | |||||||||
| Collection: | CaltechAUTHORS | |||||||||
| Deposited By: | Tony Diaz | |||||||||
| Deposited On: | 20 Mar 2019 17:16 | |||||||||
| Last Modified: | 16 Nov 2021 17:02 |
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