LAND SUBSIDENCE CAUSED BY THE EAST MESA GEOTHERMAL-FIELD, CALIFORNIA,OBSERVED USING SAR INTERFEROMETRY

Interferometric combination of pairs of synthetic aperture radar (SAR) images acquired by the ERS-1 satellite maps the deformation field ass ociated with the activity of the East Mesa geothermal plant, located i n southern California. SAR interferometry is applied to this flat area without the need of a digital terrain model. Several combinations are used to ascertain the nature of the phenomenon. Short term interferog rams reveal surface phase changes on agricultural fields similar to wh at had been observed previously with SEASAT radar data. Long term (2 y ears) interferograms allow the study of land subsidence and improve pr ior knowledge of the displacement field, and agree with existing, spar se levelling data. This example illustrates the power of the interfero metric technique for deriving accurate industrial intelligence as well as its potential for legal action, in cases involving environmental d amages.