Real-time GNSS seismology using a single receiver

SUMMARY High-rate GNSS has attracted increasing attention and numerous applications in geohazard monitoring and early warning. In this paper, we investigate three current existing singlereceiver approaches for real-time GNSS seismology, comparing their observation models for equivalence andassessingtheimpactofmainerrorcomponents. Weproposesomerefinements to the variometric approach and especially consider compensating the geometry error component by using the accurate initial coordinates before the earthquake to eliminate the drift trend in the integrated coseismic displacements. After careful corrections of satellite ephemeris, ionospheric delay, tropospheric delay and geometry errors, the refined variometric approach andthetemporalpointpositioning(TPP)methodhaveequivalentmathematicalmodelwiththe converged precise point positioning (PPP). We evaluated the precision of the variometric and TPP approaches with various error correction schemes and duration time using numerous data sets and demonstrated that few centimetres accuracy of coseismic displacements is achievable even for 20 min interval. We applied these single-receiver approaches to process 1 Hz GPS data collected from the Tohoku-Oki earthquake (Mw 9.0, 2011 March 11) in Japan to capture coseismic displacement, and further, inverted the obtained displacement fields for fault slip distribution and moment magnitude. Comparisons of the results obtained using the refined variometric approach and TPP, as well as the converged PPP, displayed very good consistence both in coseismic displacements within few centimetres and in the slip distribution patterns and moment magnitudes.