Seasonal deformation at station POVE. (a) North-East-Up components time series from our processing, detrended after outlier elimination. The time series are highlighted by a Vondrak filter of cutoff frequency 25 cpy (black line). (b) Lomb-scargle periodogram of the detrended and cleaned time series over the displayed period of observation. Expected periods are represented by the vertical line (gray dashed: annual and semi-annual period; gray solid: draconitic period and harmonics; dotted line: fortnightly tidal cycle and harmonic of ~ 14 and ~ 28 days). Location of POVE is depicted in Figure 1.