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  • Küçük Resim
    Öğe
    Determination of periodic deformation from InSAR results using the FFT time series analysis method in Gediz Graben
    (Springer Science and Business Media B.V., 2023) Hastaoğlu, K.O.; Poyraz, F.; Erdoğan, Hediye; Tiryakioğlu, I.; Özkaymak, C.; Duman, H.; Gül, Y.; Güler, S.; Doğan, A.
    Permanent Scatterers (PS) point velocities obtained by the interferometric synthetic aperture radar (InSAR) method are generally determined using the linear regression model, which ignores periodic and seasonal effects. In this study, software was developed that can detect periodic effects by applying fast Fourier transformation (FFT) time series analysis to InSAR results. Using the FFT time series analysis, the periodic components of the surface movements at the PS points were determined, and then the annual velocity values free from periodic effects were obtained. The study area was chosen as the Gediz Graben, a tectonically active region where aseismic surface deformations have been observed in recent years. As a result, using the developed method, seasonal effects were successfully determined with the InSAR method at the PS points in the study area with a period of 384 days and an average amplitude of 19 mm. In addition, groundwater level changes of a water well in the region were modeled, and 0.93 correlation coefficient values were calculated between seasonal InSAR displacement values and water level changes. Thus, using the developed methodology, the relationship between the tectonic movement in the Gediz Graben in Turkey and the seasonal movements and the change in the groundwater level was determined.
  • Küçük Resim
    Öğe
    Investigating the effects of groundwater level changes on GNSS observations in the Konya Closed Basin
    (Universidad Nacional de Colombia, 2022) Erdoğan, Hediye; Oktar, Osman; Gezgin, Cemil; Poyraz, F.; Arslan, N.; Yılmaztürk, F.
    The Konya Closed Basin (KCB), inhabited by approximately 4 million people, has a semi-arid climate and has been an important agricultural and economic production area with its fertile alluvial soils. In recent years, groundwater use as a primary source in the intense need for irrigation due to climate change, drought, and wrong agricultural policies triggered land subsidence in the basin by causing the aquifer system compaction. In this study, the effects of groundwater level changes obtained from groundwater monitoring stations on the positions of continuously operating GNSS stations located in KCB were investigated by time series analysis. As a result of trend component analyses of time series processed based on the ITRF08 fixed frame, it was determined that the horizontal positions of stations in this region were moving in the northeast direction (18.74 mm/year). For the up coordinates, while stations ANRK, KLUU, and NIGD had movements 0.56 mm/year in the up direction, the other stations moved in the down direction. The vertical movement of the KNY1 station based on 560-day data was in the down (-) direction, with an annual movement of 70.96 mm, and this was the maximum movement or velocity compared to the other stations in this region. The trend analysis of 19 wells revealed linear groundwater level changes in the down direction with a mean value of-39.22 cm/year. The decrease in the water level of the wells in the Konya Closed Basin was statistically significant for the majority of the wells and at meter level in some wells.