Global Navigational Satellite System Seismic Monitoring

ABSTRACT We have developed a global earthquake deformation monitoring system based on subsecond-latency measurements from ∼2000 existing Global Navigational Satellite System (GNSS) receivers to rapidly characterize large earthquakes and tsunami. The first of its kind, this system complements traditional seismic monitoring by enabling earthquake moment release and, where station density permits, fault-slip distribution, including tsunamigenic slow slip, to be quantified as rupture evolves. Precise point position time series from globally distributed GNSS stations are continuously estimated within an Earth center of mass-fixed reference frame and streamed as local north, east, and vertical coordinates with 1 s updates and global subsecond receiver-to-positions latency. Continuous waveforms are made available via messaging exchanges to third-party users (U.S. Geological Survey, National Oceanic and Atmospheric Administration, network operators, etc.) and internally filtered to trigger coseismic offset estimation that drive downstream point-source and finite-fault magnitude and slip characterization algorithms. We have implemented a corresponding analytics system to capture ∼100 million positions generated per day per thousand global stations positioned. Assessed over one typical week using 1270 globally distributed stations, the latency of position generation at a central analysis center from time of data acquisition in the field averages 0.52 s and is largely independent of station distance. Position variances from nominal in north, east, and vertical average 8, 9, and 12 cm, respectively, predominantly caused by random-walk noise peaking in a ∼4–5min spectral band introduced by global satellite clock corrections. Solutions completeness over the week within 0.5, 1, and 2 s latency is 55%, 90%, and 99%, respectively. This GNSS analysis platform is readily scalable, allowing the accelerating proliferation of low-cost phase-tracking GNSS receivers, including those increasingly embedded in consumer devices such as smartphones, to offer a new means of characterizing large earthquakes and tsunami far more quickly than existing systems allow.