Atmospheric effects in SAR interferometry, implications on interpretation and modeling surface deformation: A case study of the 1999 (MW=7.4) Izmit earthquake, Turkey

We show in this study that the coseismic interferograms of the 17 August 1999 Izmit, Turkey earthquake include atmospheric signal correlated with topography. The phase-elevation ratio decreases with increasing elevation, reaching up to 10 cm of relative phase delay. Although the phase-elevation ratio also varies laterally, a simple, horizontally uniform model for atmospheric effects is calculated using a digital elevation model. Correction of the observed interferograms with this model reveals that some of the anomalies in the fringe pattern, which were previously interpreted to be the sign of triggered slip, are most probably due to the changes in atmospheric conditions. The model also reveals some large scale artefacts previously undetected.