Noise and velocity field analysis of crustal movement in Anhui province

Global Navigation Satellite System (GNSS) coordinate time series contains significant information on plate movement and crustal deformation. Through using GAMIT/GLOBK software, we obtained the coordinate time series of Anhui Continuously Operating Reference System (AHCORS) from 2013 to 2018.5. Then power spectral density method and the maximum likelihood estimation method were applied to determine the optimal noise model of AHCORS for the first time. Our results show that the White Noise plus Flicker Noise (WN+FN) model represents the best model for this region. We then solved the linear trend of the obtained coordinate time series using CATS software. Overall, the velocity uncertainty with colored noise is 7 ~ 10 times of that with white noise only, while the average horizontal velocity based on the Eurasian plate is 6.43 mm/a during this period, with a direction of E29.10°S. With respect to the vertical velocity, there is a tendency of subsidence in the north and uplift in the south, with maximum subsidence reaching up to 32.82 mm/a, which appears at station SZDS in Dangshan, Suzhou. The rapid subsidence at this area is most likely due to extraction of groundwater and mineral resources in recent years.