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Geophysical Applications of Interferometric Synthetic Aperture Radar

John Dawson 1,2 and Paul Tregoning 1

1 Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia
2 Geoscience Australia

Interferometric Synthetic Aperture Radar (InSAR) is a high resolution imaging technique.  InSAR is used to both estimate surface topography and precise temporal surface deformation from satellite observations.

Our research has focused on temporal image stacking applied to the observation of 'slow' (~1mm/yr) deformation processes and the application of new modelling techniques to regions where InSAR is known to not work as effectively, including humid, heavily vegetated regions, and areas with significant agricultural activity. The principal motivation and contribution of our research is to: a) demonstrate, 'tune' and develop new temporal InSAR analysis techniques, for the observation of 'slow' geophysical deformation phenomena in InSAR-adverse regions; and b) improve the accuracy, precision and computational efficiency of these techniques.

We have made the first InSAR observations of coseismic deformation on the Australian continent, including magnitude 4.4 and 4.8 earthquakes in the South West Seismic Zone of Western Australia (Fig. 1).  We have also tested the new ALOS PALSAR sensor, launched in 2006, for characterizing topography and surface deformation (Fig. 2).  Our research will now focus on quantifying the spatial and temporal deformation of the Perth basin, associated with ground water extraction.

Figure 1.  Magnitude 4.8, 10/10/2007 Katanning, Western Australia, earthquake: observed and modelled (L-Band) interferograms. Each fringe (or full color cycle) represents the line-of-sight range change of one half of the radar instrument wavelength (i.e. 0.118 m), the wavelength of the ALOS PALSAR instrument was 0.236 m. The ascending pass line-of-sight (target to satellite) unit vector was -0.596, -0.139, 0.792 in the east, north and up components respectively. A) Observed interfergram. B) Computed line-of-sight deformation along profile A-B. C) Modelled interferogram. D) Modelled line-of-sight deformation along profile A-B (observed repeated in red). E) Observed minus modelled interferogram. F) Observed minus modelled along profile A-B. 

Figure 2.  Topography estimated from ALOS PALSAR observations.  Resolution is 15 metres.