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Abstract:
GNSS observations are available at a high temporal frequency and accuracy. Their usefulness in capturing coseismic deformation during large earthquakes is here tested. Precise point positioning (PPP) is used to compute coordinate time series for 61 stations of the TUSAGA-Aktif network during the 2023 earthquake sequence. Precise GPS, GLONASS and Galileo satellite orbits and clock offsets computed by GFZ are used, together with GNSS observations with a sampling interval of 1 s, 30 s or 5 minutes. The difference between postseismic and averaged preseismic coordinates provides displacement time series with generally centimeter-level horizontal accuracy. The time series computed with a 5 minute temporal sampling rate captures coseismic displacement greater than nominal uncertainties at a few stations, peaking at ~30 cm on either side of the East Anatolian Fault (EAF) for the largest shock (Mw 7.8) and at ~4 m for the Mw 7.5 event, which occurred on a fault very close to station EKZ1. The time series computed every 30 s and (using interpolated satellite clock offsets) every 1 s show no evidence of significant pre/post-seismic creeping. Estimates of coseismic displacement from PPP GNSS solutions are compared with those from seismology and InSAR. Although the sensitivity of these solutions with high sampling rates can only capture significant coseismic displacement, this work serves as a preliminary exploration of a future system for automatic near-real-time imaging of surface displacement during ruptures capable of detecting complex sequences of ruptures and creeping.
