The USGS Southern California GNSS Network - Modernization and Collaboration for Reliable Data Streams to Enhance Earthquake Early Warning Applications

The U.S. Geological Survey's Southern California GNSS Network is in the process of a major overhaul to modernize both data collection equipment and telemetry. The goals of this upgrade are both to provide the seismo-tectonic research community with the best possible data from these long-operating continuous GNSS stations and to contribute reliable, high-quality geodetic data streams to California's nascent Earthquake Early Warning System, ShakeAlert. Plans are underway to upgrade nearly a hundred existing GNSS receivers across the network (~⅔ of the stations) over the next year, replacing 14-year-old receivers with new receivers configured for onboard Precise Point Positioning and multiple constellations. Older choke ring antennas are being replaced as well to maximize GNSS signals beyond GPS. Modern receivers and high sampling rate data require robust telemetry and where current hardware is inadequate, upgrades are also being performed using much higher bandwidth 5.8GHz radios and LTE cellular modems. Data streaming performance, including latencies, can be monitored in real time online. One sample-per-second positions, computed with commercially available software that processes streaming GPS data using Precise Point Positioning, are transformed in real time to an open GIS file format and made available via an open-source message-broker, from which they can be accessed by ShakeAlert processing centers as well as research groups developing geodetic algorithms for Earthquake Early Warning.