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Evaluation of the displacements of the permanent GPS stations of Beni Haroun Dam geodetic network (Algeria)

Khelifa Sofane, Dekkiche Hicham, Kahlouche Salem, Boudina Samia

Acta Geophysica

2021

Vol. 69, no. 6

2129--2143

The purpose of this paper is the analysis of the daily coordinate time series of the five permanent GPS (Global Positioning System) stations of the geodetic monitoring network of the Beni-Haroun Dam (Algeria), in order to assess the spectral content of the dam displacements. The coordinate time series analysis was based on the singular spectrum analysis to assess their principal components (trend, seasonal components and noise in phase space), the spectral analysis to identify their noise spectrum (white or colored) and the wavelet thresholding method to determine their noise in frequency space. The results showed that the primary signal present in the analyzed time series is mainly composed of a trend and an annual component. The trend and the annual signal explain more than 95% of the total signal in the three coordinates (x, y, z) for all studied stations. The analyzed time series in the three coordinates (x, y, z) are characterized by a linear drift less than 1 mm/year, their annual amplitudes are in the range of 0.5–2 mm, and the amplitudes of their semiannual, four-monthly and quarterly signals are in the range of 0–0.5 mm. The noise spectrum in the analyzed time series is flicker noise, and the noise level is in the range of 0.2–0.7 mm, 0.3–0.5 mm and 0.5–1.2 mm in, respectively, x-, y- and z-coordinates. The low values of trend and noise level in the analyzed station coordinates indicate that the Beni-Haroun Dam is qualified as stable.