Crustal deformation in Australia measured by satellite radar interferometry using ALOS/PALSAR imagery

The Advanced Land Observing Satellite (ALOS), launched on 24 January 2006, is a Japanese satellite carrying an L-band SAR sensor, namely the PALSAR, which is expected to demonstrate good performance in applications such as crustal deformation measurement, subsidence detection and landslide monitoring. This paper describes a case study of Differential Synthetic Aperture Radar Interferometry (DInSAR) using ALOS/PALSAR data to detect crustal deformation caused by a recent small earthquake in Western Australia. Single Look Complex (SLC) images acquired by the ALOS/PALSAR sensor were used to measure the co-seismic deformation of the 9 October 2007 earthquake that occurred south of the town of Katanning, in the state of Western Australia. Three images with dual polarizations (HH & HV) were used in this study; two acquired before the earthquake event and one after. The two-pass DInSAR processing method was applied to generate differential interferograms. The peak-to-peak surface displacement is up to 32 centimetres in the radar line-of-sight direction. The interferograms were used to constrain the fault modelling. The co-seismic displacements were modelled using a two-segment uniform slip model in a homogeneous isotropic half-space. A genetic algorithm was used to determine the optimal source parameters for the nonlinear inversion. The resultant maximum slip is about 0.4 metres on an almost pure reverse fault striking PNE55 degrees and dipping at P40 degrees S. The scalar moment was estimated to be 1: 84 x 1016 Nm(Mw4.8), which is in good agreement with the seismological results. The root-mean-square difference between the DInSAR observed and modelled displacements is 1.6 cm.