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The U.S. Geological Survey Southern California GNSS Network: Improving Real-time Data Acquisition and Analysis for Hazard Monitoring and Earthquake Early Warning

The U.S. Geological Survey’s 142-station Southern California GNSS Network (SCGN) is undergoing a major overhaul to both modernize data collection equipment and telemetry and improve real-time data acquisition and analysis. These efforts will support long-term monitoring and earthquake early warning (EEW). Over the next year, nearly 100 of the SCGN stations will be equipped with new receivers configured with onboard precise point positioning (PPP) and new choke ring antennas to allow multiple-GNSS signal tracking. The telemetry at many stations will also be upgraded to use higher bandwidth 5.8 GHz radios and LTE cellular modems to provide robust real-time streaming of 1-Hz data for both data archiving and real-time processing. Data streaming performance and latencies can be monitored online in real time (https://scign.org). One-Hz PPP positions from both onboard and commercially available software are converted in real time to the open standard geoJSON format and made accessible via an open-source message-broker to the USGS ShakeAlert project, an EEW system being developed for the west coast of the U.S. The ShakeAlert GNSS data providers are currently assessing static and dynamic data quality metrics and position solution comparisons in order to provide a robust GNSS data product for event characterization.

Our real-time PPP analyses estimated the dynamic and static offsets of the M7.1 2019 Ridgecrest mainshock at the several-cm level, with maximum horizontal peak ground displacement of 700 mm at a station located 20 km from the epicenter. Observed peak ground displacements in our analysis of 9 nearby stations could have provided a M7.0 event warning within 23 s of the origin time, which compares favorably with the seismic data warning performance. We will discuss our efforts to improve real-time solution precision and latencies using multiple-GNSS observations and to expand our processing capabilities to include over 1000 west coast GNSS stations.

Presenting Author: Mark H. Murray

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