Crustal deformation after 2004 niigataken-chuetsu earthquake, central Japan, investigated by persistent scatterer interferometry

In order to precisely measure the displacement field after the 2004 Niigataken-Chuetsu earthquake, central Japan, we performed a persistent scatterer (PS) interferometry analysis on SAR images acquired by the European satellite ENVISAT. After performing a PS interferometry analysis, we first corrected for artifacts due to orbit inaccuracies and atmospheric phase delay using GPS displacements. This post-processing revealed that the dominant component of the displacements is a seasonal pattern caused by water extraction during winter. Precise estimation of the tectonic component of the displacements, which enables discussion of the order of 1 cm displacements and 1 cm/year velocity, was further obtained by separating out the seasonal component using a principal component analysis. A part of observed signals was consistent with deformations due to afterslips and poroelastic relaxation of the 2004 earthquake. Another part of the signals was consistent with a relative motion of two blocks whose boundary coincides with the Western Nagaoka Plain faults.