GSeisRT: A precise point positioning software to capture ground deformations for geohazards in real time using GPS/BeiDou/GLONASS/Galileo/QZSS observations

For earthquake early warning, precise coseismic displacement waveforms are necessary in real time for decision makers to issue alerts for the public safety and infrastructure shutdown. Real-time Global Navigation Satellite System (GNSS) has been a valuable tool to continuously monitor seismic motions where permanent displacements can be achieved unambiguously. As a dedication to the seismic community, the GSeisRT software developed by Wuhan University can realize multi-GNSS (GPS/GLONASS/GALILEO/QZSS/BeiDou) precise point positioning ambiguity resolution (PPP-AR) and achieve centimeter-level to sub-centimeter-level precision in real time. While a stable maintenance of a global PPP service is still challenging, this software is capable of estimating satellite clocks and phase biases in real time using a regional network by fixing IGS (International GNSS Service) ultra-rapid orbit products. Such capability makes GSeisRT especially suitable for those proprietary regional GNSS networks, and more importantly, the highest possible positioning precision can be more consistently obtained. We have applied this software platform to the Crustal Movement Observation Network of China (CMONOC, 260 stations), the Network of the America of the USA (NOTA, 950 stations) and the Chilean GNSS Network in collaboration with China Earthquake Administration (CEA), UNAVCO, USA and National Seismological Center (CSN) of Chile. Several earthquake events (2020 Oaxaca Mexico M7.4 earthquake, 2020 Lone Pine California M5.8 earthquake, etc.) have been captured successfully in real time by GSeisRT. The real-time results showed good precision of about 1 cm, thanks to the multi-GNSS data, and they were in good agreement with the post-processing results. With a PGD (Peak Ground Displacement) analysis, the real-time earthquake magnitude estimates for the Oaxaca Mexico event and the Lone Pine California event are M7.2 and M5.7, respectively. GSeisRT software is dedicated to real-time seismic monitoring and it is free and open for the science community under mutual agreement.