Real-Time Seismic Waveforms Estimation of the 2019 MW=6.4 and Mw=7.1 California Earthquakes With High-Rate Multi-GNSS Observations

Global Navigation Satellite System (GNSS) is recognized as an effective tool to retrieve high-precision seismic displacements, which has been widely used in earthquake early warning systems such as magnitude estimation and fault slip inversion. In this study, we present two multi-GNSS positioning models for rapidly capturing real-time coseismic displacements using the raw pseudorange, carrier phase and Doppler measurements, called constant velocity (CV) and constant acceleration (CA) dynamic precise point positioning (PPP) models, respectively. The proposed methods are validated with the datasets collected during the 2019 July 4 M-w 6.4 and July 6 M-w 7.1 earthquakes in real-time scenarios. Results show that the two models can provide accurate displacement waveforms with the accuracy of few centimeters. Besides, the multi-GNSS integration can significantly improve the model performances compared with GPS-only solutions in both time- and frequency- domains. The dynamic PPP models can also reliably recover the moment magnitudes and permanent seismic displacements, indicating that the methods have the potential to benefit for earthquake early warning and rapid geohazard assessment.