The Importance of Atmospheric Corrections on InSAR Surveys Over Turkey: Case Study of Tectonic Deformation of Bodrum-Kos Earthquake

Abstract

The Bodrum-Kos earthquake which occurred on 20th July 2017 at 1:31 am local time with a magnitude of Mw 6.6 in the Gulf of Gokova in Turkey. The Bodrum-Kos earthquake caused a small radius tsunami in Bodrum coast and its surroundings. Here, the Interferometric Synthetic Aperture Radar (InSAR) method was utilized to reveal tectonic deformation caused by the Bodrum-Kos earthquake. The InSAR technique was increasingly used to detect ground deformation such as landslide, tectonic or volcanic. In this study, the crucial atmospheric corrections which are GACOS and phase-elevation corrections on InSAR data are discussed. GACOS correction is based on high-resolution European Centre for Medium-Range Weather Forecasts weather model at 0.125° and 6-h resolutions, SRTM DEM and ASTER GDEM. GACOS is used to separate stratified and turbulent signals from tropospheric total delays and generate high spatial resolution zenith total delay maps to be used for correcting InSAR measurements and other applications. Phase-elevation linear correction is also used to separate mostly stratified signals from tropospheric total delays due to the topographic elevation changes and 3 arc second topographic map was used in the phase-elevation correction. These atmospheric correction methods were tried both separately and sequentially and standard deviations of each method were presented. The points comparison of the cumulative line of sight displacement maps were made after and before correction. The point on the Karaada (C point) shows subsidence after the earthquake and then recovers again. Time-series results of all points show similar values until the earthquake occurs. Time-series result also shows that the Bodrum-Kos earthquake has a small radius effect over the land area only the north and maybe west island due to the occurrence on the sea and lost its much energy without reaching the land.