Noise Characteristics of Operational Real‐Time High‐Rate GNSS Positions in a Large Aperture Network

Large earthquakes are difficult to model in real-time with traditional inertial seismic measurements. Several algorithms that leverage high-rate RT-GNSS positions have been proposed and it has been shown that they can supplement the earthquake monitoring effort. However, analyses of the long-term noise behavior of high-rate RT-GNSS positions, which are important to understand how the data can be used operationally by monitoring agencies, have been limited to just a few sites and to short time spans. Here we show results from an analysis of the noise characteristics of one year of positions at 213 RT-GNSS sites spanning a large geographic region from Southern California to Alaska. We characterize the behavior of noise and propose several references noise models which can be used as baselines to compare against as technological improvements allow for higher precision solutions. We also show how to use the reference noise models to generate realistic synthetic noise that can be used in simulations of HR-GNSS waveforms. We discuss spatiotemporal variations in the noise and their potential sources and significance. We also detail how noise analysis can be used in a dynamic quality control to determine which sites should or should not contribute positions to an earthquake modeling algorithm at a particular moment in time. We posit that while there remain important improvements yet to be made, such as reducing the number of outliers in the time series, the present quality of real-time HR-GNSS waveforms is more than sufficient for monitoring large earthquakes.