Abstract
Abstract. Atmospheric phase contribution significantly influences co-seismic surface deformation estimates from repeat pass Differential Synthetic Aperture Radar Interferometry (DInSAR). Present study investigates the contribution of the atmosphere in co-seismic deformation estimation associated with the 20 April 2013 Lushan (China) earthquake. The Lushan Earthquake occurred in the south-western segment of the Longmenshan fault zone, on the eastern margin of the Qinghai-Tibetan Plateau. Using pre- and postearthquake Radarsat-2 interferometric pair, the co-seismic deformation of the Lushan earthquake has been estimated. The tropospheric phase delay component has been estimated using tropospheric models in conjunction with surface temperature and pressure data from MODIS atmospheric products. The ionospheric phase component has been computed using the Total Electron Content (TEC) data. The net atmospheric path addition in the study area varies from 3.022 m to 4.621 m for the pre-earthquake SAR acquisition and from 2.687 m to 4.199 m for the post-event data acquisition. Comparison of the Line of Sight (LOS) displacement values computed using un-corrected and corrected interferometric data shows that the atmospheric phase component has introduced considerable contribution in the LOS displacement values. The uncorrected LOS displacement values vary from 0.902 m to −0.157 m where as those from the phase-corrected interferometric data are in the range of 0.052 m and −0.062 m. The corrected LOS displacement values show close agreement to a few GPS based co-seismic surface deformation components from published literature. Thus removal of atmospheric phase contribution is a necessary step in using repeat pass DInSAR for co-seismic surface deformation estimation.
Highlights
Differential SAR interferometry is one of the cost effective techniques in quantifying surface deformations associated with various tectonic or anthropogenic processes
The present study evaluates the influence of atmosphere in introducing path delay during SAR acquisitions and thereby causing additional component in the co-seismic displacement values estimated using repeat pass Differential Synthetic Aperture Radar Interferometry (DInSAR) technique
Due to the non-availability of an interferogram from SAR data of short temporal spacing, excluding the seismic event, external digital elevation model (DEM) (SRTM V.4.3, 3-arc-second) was used to remove the topographic phase so that the residual phase is due to the co-seismic deformation
Summary
Differential SAR interferometry is one of the cost effective techniques in quantifying surface deformations associated with various tectonic or anthropogenic processes. There are extraneous factors that often bring about phase changes amongst multiple SAR acquisitions. These are variations of atmospheric conditions, coherence variations associated with temporal variations of the targets and decorrelation caused by baseline changes. The state of the atmosphere in terms of the pressure, temperature and water vapour, which influence the refractive index of the medium are the prime factors in determining the tropospheric path delay (Ding, 2008). The ionosphere causes propagation advancement of the signals and depends on the total electron content (TEC) in the ionosphere. In both the cases, the path delay is influenced by the wavelength of the signals
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