Application of SAR interferometry to a geothermal field

Abstract

To measure the land deformation, we applied SAR interferometry to a geothermal field, where a geothermal plant has operated since 1995. Interferometric fringes were generated by the difference in radar phase acquired at different times by the JERS-1 SAR. We constructed interference patterns from the difference of two pairs of SAR images of `94/09/19-`95/04/27 and `95/04/27-`95/09/06. The coherence of the `94/09/19-`95/04/27 pair is degraded probably by the spatial baseline noise. The interference patterns partly suffer from a spatial change of moisture. To evaluate the results, we compare the interferometric fringes of `95/04/27-`95/09/06 pair with the level changes during 1994 ? 1995 observed by leveling. The leveling shows a local subsidence of several centimeters. There is a good correlation in the comparison, however, the amplitude of the leveling during September 1994 ? October 1995 is about two times greater than the slant range of interferometry. I interpret that the ground has been subsiding constantly during September 1994 ? October 1995 and that the interferometric fringes correspond to the land deformation in the order of cm during about a half period of the leveling observation.