Latency of Waveform Data Delivery from the Southern California Seismic Network during the 2019 Ridgecrest Earthquake Sequence and Its Effect on ShakeAlert
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1.
California Institute of Technology
Abstract
The occurrence of the 4–6 July 2019 M_w 6.4 and M_w 7.1 Ridgecrest earthquake sequence provided the first full‐scale test of the network and telemetry readiness of the Southern California Seismic Network (SCSN), to support the ShakeAlert earthquake early warning (EEW) system in California. ShakeAlert is a U.S. Geological Survey (USGS)‐led collaboration to detect earthquakes and, when possible, to alert the public before the arrival of the strongest shaking. The SCSN performed well in its regional monitoring role for both the 4 July M_w 6.4 and the 6 July M_w 7.1 earthquakes. In the EEW role, it provided timely delivery of 5 s of P‐wave data to ShakeAlert, which issued its first alert 6.9 s after origin time. Data delivery at peak data volumes for many stations exhibited some latency, and, as a consequence, some data arrived too late for analysis by one of the EEW algorithms. We find that the average link bandwidth for each station was sufficient, because all waveform data were delivered automatically to the archive, but link capacity for many stations was insufficient for peak demand. We describe the performance of the data telemetry for the sequence, including cellular, radio, hybrid, and backhaul systems. Cellular‐based telemetry systems maintained low latency throughout strong shaking and after, but some stations, even at great distances, experienced subsequent brief increases in latency. Performance of radio links depended mostly on the signal strength of the link, with short‐distance direct shots to high‐bandwidth backhaul systems showing no latency impact, whereas stations on some long distance or marginal quality links suffered latencies of tens or hundreds of seconds. Improvements are being implemented to move telemetry links onto USGS and partner high‐bandwidth microwave systems, and to reduce dependency on less robust long‐distance radio shots.
Additional Information
© 2020 Seismological Society of America. Manuscript received 3 June 2020; Published online 18 November 2020. The Southern California Seismic Network (SCSN) is supported by the U.S. Geological Survey and Advanced National Seismic System (USGS and ANSS) through the USGS Pasadena Office and through Cooperative Agreements to Caltech. The SCSN is partially funded by USGS Cooperative Agreements (G15AC00023 and G19AS00034), Gordon and Betty Moore Foundation Grant 5229 to Caltech, and California Office of Emergency Services (Cal OES) Agreement 6012‐2017 with Caltech. The authors recognize numerous USGS, Caltech, and other staff members who contribute to the operations of the SCSN. In particular, the authors would like to thank the SCSN operations team consisting of A. Aspiotes, C. Bruton, A. Cadiao, A. Devora, P. Hegarty, B. Jones, S. Lydeen, B. McDowell, J. Ramsay, D. Sutton, V. Thomas, A. Good, and M. Watkins. The authors also thank National Earthquake Information Center (NEIC), Albuquerque Seismological Laboratory (ASL), and the staff of the Geothermal Program Office at the Naval Air Weapons Station China Lake for their collaboration. The authors acknowledge partner networks including the California Geological Survey and the National Strong Motion Instrumentation Program, Southern California Edison, and Pacific Gas and Electric that share real‐time data with the SCSN from over 150 stations. 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: The Southern California Seismic Network (SCSN) seismic data latency was collected with an Earthworm (http://www.earthwormcentral.org, last accessed March 2020) module that was designed and written at Caltech. The latency data are not served by SCSN web services but available from the authors. Seismograms used in this study were collected as part of the SCSN. Data partially can be obtained from the Incorporated Research Institutions for Seismology (IRIS) Data Management Center at www.iris.edu (last accessed September 2020) or using the SCSN webservices at https://scedc.caltech.edu (last accessed September 2020). The plots were made using the Generic Mapping Tools version 5.4.0 (www.soest.hawaii.edu/gmt, last accessed September 2020; Wessel and Smith, 1991).Additional details
- Eprint ID
- 106806
- Resolver ID
- CaltechAUTHORS:20201124-101236620
- G15AC00023
- USGS
- G19AS00034
- USGS
- 5229
- Gordon and Betty Moore Foundation
- 6012‐2017
- California Office of Emergency Services
- Advanced National Seismic System (ANSS)
- Created
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2020-11-24Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Seismological Laboratory