The Utility of Synthetic Aperture Radar (SAR) Interferometry in Monitoring Sinkhole Subsidence: Subsidence of the Devil's Throat Sinkhole Area (Nevada, USA)

Synthetic Aperture Radar (SAR) interferometry, a newly progressed technique capable of detecting very small ground surface elevation changes, was proposed to detect and monitor sinkholes subsidence susceptibility over large karstic areas. This technique, which was proposed by researchers in the area of geophysical studies in 1989, uses (SAR) images to measure very small (1cm or less) surface motion over large areas with good spatial resolution (tens of meters). The advanced method has been used in the studies of earthquakes and other natural phenomenon and has shown promising results. The effectiveness of the remotely sensed technique in determining the damage caused by sinkholes is assessed by using a simplified model approximated by the normal probability (Gaussian) distribution theory proposed by researchers in 1969 to study the mechanism of the resulting ground surface subsidence, estimate the order of magnitude of such settlement and finally determine whether these settlements are sufficiently large to be detected by InSAR. A specific purpose database, including both collapse and subsidence sinkholes, was developed to store and organize all the important information relative to different case histories. This information was used to further investigate the relevance of SAR interferometry in studying the phenomenon. The relevance of the proposed technique was further investigated by utilizing three European Remote Sensing (ERS) Synthetic Aperture Radar (SAR) images encompassing an almost 5-year period of observation (1992–1997), three successful interferograms with short perpendicular baseline (>100 meters) from a descending orbital trajectory have been produced. Analysis of these interferograms indicate a relative regional subsidence of up to 0.5 cm/year within the Devil's Throat Sinkhole area, located in the Gold Butte district of Clark County in the Southeast corner of Nevada. Observations of deformation along profiles constructed on the produced interferograms also show a steep gradient in displacement rates occurring very close to the area where the Devil's Throat Sinkhole exists. The demonstration of the technique in the Devil's Throat area, applied using data from the European Space Agency's ERS systems, has shown promising and unique results. These results demonstrate the effectiveness of the technique in studying small-scale ground deformations over large karstic areas.