Coseismic and postseismic deformation estimation of the 2011 Tohoku earthquake in Kanto Region, Japan, using InSAR time series analysis and GPS

• We studied the Kanto area deformation during and after the 2011 Tohoku earthquake.
• We combined InSAR and GPS to estimate accurate, time variant deformation.
• We used 6 images and 1 GPS station to estimate deformation maps with RMSE of 6.9 mm.
• We identified a differential postseismic deformation pattern.

We propose a methodology using interferometric synthetic aperture radar (InSAR) time series analysis and a single GPS station to estimate the coseismic and postseismic crustal deformations in the Kanto region, Japan, which has been affected by the 2011 Tohoku earthquake. The proposed methodology depends on choosing a proper deformation trend(s) to accurately describe the earthquake deformation signature by studying the deformation time series of a single GPS station. The modeled deformation trend is subtracted from the unwrapped phase maps to separate the main deformation signature from the imposed errors. Some deformation components, not described by the model(s), will leak to the residual phase maps which will be subjected to temporal and spatial filtering. The final corrected unwrapped phase maps are estimated by restoring the modeled deformation trend to the filtered residual phase maps and finally the deformation time series is estimated using a least squares technique. The proposed methodology was designed to retrieve complex and fine surface deformations in areas that have been affected by large dominating deformation signatures and contain at a least single GPS station. The methodology was tested using Envisat-ASAR C-band images and validation was carried out using GPS stations resulting in a mean RMS error of 6.9 mm. The estimated deformation time series shows a differential postseismic deformation pattern that can be attributed to an off Boso peninsula motion triggered by the 2011 Tohoku earthquake.