Interferometric SAR for Geology Applications

One of the key applications of SAR is based on the fact that phase information is retained/required during processing of the imagery. As a result, it is possible to use the phase information as a sensitive measurement tool for changes in position across the image. Known generically as SAR interferometry, or InSAR, this family of techniques enables the measurement of topographic height, changes in topographic height, and changes in scattering properties within a SAR scene.

An important application of InSAR is the measurement of ground motion. Differential SAR interferometry (DifSAR) was initially demonstrated as an important tool in the observation of tectonic and volcanic deformation, as well as monitoring ice motion.

On December 26, 2003, a magnitude 6.6 earthquake struck very near the city of Bam Iran. Due to the extensive number of adobe structures in the city, this earthquake leveled almost all of the city. Several tens of thousands of lives were lost. It was not until the SAR data from the European Envisat satellite were processed that the actual location of the earthquake epicenter and associated fault were discovered. There was no surface rupture or other evidence at this location.

Neva Ridge has processed the original Envisat data (left). Surface motion structured into four lobes is observed. There is both subsidence and rising of terrain around the epicenter. The fringes shown indicate about a 30-centimeter shift towards the SAR for the south-east lobe and about a 15-centimeter subsidence away from the SAR in the north-east lobe. The eastern lobes show significantly less motion (~ 5 cm).

For more information, contact David Cohen