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MEASUREMENT OF SURFACE DISPLACEMENT CAUSED BY UNDERGROUND NUCLEAR EXPLOSIONS BY DIFFERENTIAL SAR INTERFEROMETRY

Differential synthetic aperture radar Interferometry (DInSAR) has nowadays become an important means for measuring and monitoring of surface displacements of various types. This paper focuses on investigating the capability of this technique for detection and characterization of past underground nuclear explosions at the Nevada Test Site (NTS), especially the synergy with seismic data. By this analysis large scale surface subsidence phenomena were revealed, which were either related to the detonation itself or post-event deformation. Data of different kinds, namely satellite data from both ERS 1 and 2, external DEM and seismic sources etc., have been used for interferogram processing and interpretation. Because of the date limitation by the first acquired data from NTS, only few test events could be studied coseismically (i.e. from SAR data covering the period before and after the detonation); in the other cases investigations were restricted to postseismic deformation, i.e. restricted to post-event SAR data. The analysis was not limited to determination of the center of gravity of the subsidence crater, but also shape and depth of the deformation pattern were extracted. Theoretically, the amount of deformation could be measured with millimeter accuracy. But in realty, many other error sources must be taken into account, such as atmospheric effects, temporal decorrelation, and noise. Although this accuracy limit is therefore hard to realize in practice, the achieved precision usually outperforms other remote sensing techniques. This work has been carried out in part within the framework of the Global Monitoring for Security and Stability (GMOSS) Network of Excellence initiated by the European Commission.