Deformation of the 1995 North Sakhalin earthquake detected by JERS-1/SAR interferometry

We present a map of the coseismic displacement field resulting from the North Sakhalin, Russia, May 28, 1995, earthquake. Raw radar signal data from the JERS-1 synthetic aperture radar instrument acquired in 28 April, 11 June, 25 July, and 7 September 1995 are used to generate a high-resolution, wide area map of the displacements by the two-pass differential interferometry method. The interferogram shows that an area of 60 km (EW) by 80 km (NS) experienced crustal deformations. The slip mechanism with fine structure is inverted using the displacement field of the SAR interferogram. This inversion of the SAR interferogram shows, 1) the rupture area extends to the south of the southernmost rupture trace on the surface, 2) slip varies from one to seven meters from the south to the northern part on the fault plane. A theoretical fringe pattern from the model of the earthquake motion matches the observations closely. We generate a full scene digital elevation model (DEM) by JERS-1 SAR interferometry and synthesize a four-pass interferogram. Comparison of the differential interferometry between the four-pass and two-pass interferograms shows that they are very similar and the both methods are reliable to show surface displacements using JERS-1 SAR. Correlation study of the Sakhalin interferograms indicates that low surface temperatures, below the freezing point, reduced the correlation probably because a freeze would alter the dielectric constant of the surface. In these Sakhalin interferograms, we find few spurious fringes due to the usual heterogeneous distribution of weather-related atmospheric and surface conditions, probably because of the low temperatures. We also present a map of the postseismic displacement field with the SAR interferometry.